In Lorraine, Christina served as adviser to her son, especially in repairing the finances of Lorraine after the war and winning the loyalty of the local nobility, and assisted her daughter-in-law as hostess.
In March 1560, she was again appointed regent of Lorraine during the absence of her son and daughter-in-law at the French court.
She was present at the coronation of Charles IX in Reims in May 1561, and of Emperor Maximilian in Frankfurt in 1562.
Her son Charles made his state entry to Nancy in May 1562 and officially took over the regency.
However, he continued to rely on Christina as his adviser in affairs of state.
In 1564, she concluded an agreement with the Bishop of Toul, by which he granted his temporalities to the Duke of Lorraine with the consent of the Pope.
As the political adviser of her son, who often preferred to delegate political tasks to her, she had a strong position in the Ducal court in Lorraine, in particular as her daughter-in-law Claude preferred to spend her time at the French court, which she often visited.
However, she was worried over the influence of the French queen dowager Catherine de' Medici, whom she suspected of trying to influence Lorraine, and in trying to disturb her relationship to her son, in an attempt to deprive her of her influence in the affairs of state.

At the death of her father, in his prison in Denmark in 1559, her elder sister Dorothea assumed the title of Queen of Denmark.
However, being a childless widow and no longer expected to be able to have children, Dorothea was no longer considered politically useful.
The Danish loyalists, headed by the exiled Peder Oxe, therefore asked Christina to persuade Dorothea to surrender her claims to Christina and her son.
Christina made Oxe a part of the Ducal council, and in 1561, she visited Dorothea, and reportedly followed his advice and convinced Dorothea to surrender her claim.
After this, Christina styled herself the rightful Queen of Denmark, Norway and Sweden.
In February 1563, she referred to herself as "Christina, by the grace of God Queen of Denmark, Sweden, and Norway, Sovereign of the Goths, Vandals, and Slavonians, Duchess of Schleswig, Dittmarsch, Lorraine, Bar, and Milan, Countess of Oldenburg and Blamont, and Lady of Tortona."

In 1561, Christina planned to marry her daughter Renata to King Frederick II of Denmark.
However, on the outbreak of the Nordic Seven Years' War between Denmark and Sweden in 1563, she interrupted these plans.
She was aided by Peder Oxe, the adventurer Wilhelm von Grumbach and his allies, who attempted to dethrone her second cousin king Frederick II of Denmark in her favour, and advised her to raise an army an invade Jutland, by which she would be welcomed by the Danish nobility, at that time in opposition to the Danish monarch.
From 1565 to 1567, Christina negotiated with king Eric XIV of Sweden to create an alliance between Sweden and Denmark through a marriage between Renata and Eric XIV.
The plan was for Christina to conquer Denmark with the support of Sweden, a plan Eric agreed to, if she could secure the support from the Emperor and the Netherlands.
In 1566, Christina struck a medal referring to herself with the title Queen of Denmark, with the motto: Me sine cuncta ruunt (Without me all things perish).
However, Emperor Ferdinand was against the plan because the destructive effect it would have of the power balance in Germany, where Saxony, being strongly allied with Denmark, opposed Christina's claims.
Nor did she manage to acquire the support of Philip of Spain.
The planned marriage alliance between Lorraine and Sweden was finally terminated when Eric XIV married his non-noble lover Karin Månsdotter in 1567.
In 1569, Christina still entertained hopes to press her claims to the Danish throne, but was met with the reply from Cardinal Granvelle, that the Netherlands would never turn against Denmark; that the Emperor would oppose it, and that Spain was occupied elsewhere.
With the end of the Nordic Seven Years' War in 1570, Christina no longer worked actively in this matter.

In June 1568,
In Lorraine, Christina served as adviser to her son, especially in repairing the finances of Lorraine after the war and winning the loyalty of the local nobility, and assisted her daughter-in-law as hostess. In March 1560, she was again appointed regent of Lorraine during the absence of her son and daughter-in-law at the French court. She was present at the coronation of Charles IX in Reims in May 1561, and of Emperor Maximilian in Frankfurt in 1562. Her son Charles made his state entry to Nancy in May 1562 and officially took over the regency. However, he continued to rely on Christina as his adviser in affairs of state. In 1564, she concluded an agreement with the Bishop of Toul, by which he granted his temporalities to the Duke of Lorraine with the consent of the Pope. As the political adviser of her son, who often preferred to delegate political tasks to her, she had a strong position in the Ducal court in Lorraine, in particular as her daughter-in-law Claude preferred to spend her time at the French court, which she often visited. However, she was worried over the influence of the French queen dowager Catherine de' Medici, whom she suspected of trying to influence Lorraine, and in trying to disturb her relationship to her son, in an attempt to deprive her of her influence in the affairs of state.
At the death of her father, in his prison in Denmark in 1559, her elder sister Dorothea assumed the title of Queen of Denmark. However, being a childless widow and no longer expected to be able to have children, Dorothea was no longer considered politically useful. The Danish loyalists, headed by the exiled Peder Oxe, therefore asked Christina to persuade Dorothea to surrender her claims to Christina and her son. Christina made Oxe a part of the Ducal council, and in 1561, she visited Dorothea, and reportedly followed his advice and convinced Dorothea to surrender her claim. After this, Christina styled herself the rightful Queen of Denmark, Norway and Sweden. In February 1563, she referred to herself as "Christina, by the grace of God Queen of Denmark, Sweden, and Norway, Sovereign of the Goths, Vandals, and Slavonians, Duchess of Schleswig, Dittmarsch, Lorraine, Bar, and Milan, Countess of Oldenburg and Blamont, and Lady of Tortona."
In 1561, Christina planned to marry her daughter Renata to King Frederick II of Denmark. However, on the outbreak of the Nordic Seven Years' War between Denmark and Sweden in 1563, she interrupted these plans. She was aided by Peder Oxe, the adventurer Wilhelm von Grumbach and his allies, who attempted to dethrone her second cousin king Frederick II of Denmark in her favour, and advised her to raise an army an invade Jutland, by which she would be welcomed by the Danish nobility, at that time in opposition to the Danish monarch. From 1565 to 1567, Christina negotiated with king Eric XIV of Sweden to create an alliance between Sweden and Denmark through a marriage between Renata and Eric XIV. The plan was for Christina to conquer Denmark with the support of Sweden, a plan Eric agreed to, if she could secure the support from the Emperor and the Netherlands. In 1566, Christina struck a medal referring to herself with the title Queen of Denmark, with the motto: Me sine cuncta ruunt (Without me all things perish). However, Emperor Ferdinand was against the plan because the destructive effect it would have of the power balance in Germany, where Saxony, being strongly allied with Denmark, opposed Christina's claims. Nor did she manage to acquire the support of Philip of Spain. The planned marriage alliance between Lorraine and Sweden was finally terminated when Eric XIV married his non-noble lover Karin Månsdotter in 1567. In 1569, Christina still entertained hopes to press her claims to the Danish throne, but was met with the reply from Cardinal Granvelle, that the Netherlands would never turn against Denmark; that the Emperor would oppose it, and that Spain was occupied elsewhere. With the end of the Nordic Seven Years' War in 1570, Christina no longer worked actively in this matter.
In June 1568,
Christina of Denmark