"Personal reasons" is often a euphemism for other things, but Solana is genuinely relinquishing the post in order to devote more time to family, notably her two year-old daughter. 
Watu wengi wanapong'atuka hutumia "sababu binafsi" kama maelezo rahisi ya kufunika sababu halisi, lakini Solana kwa hakika ameamua kuachia ngazi ili apate nafasi ya kutosha kutunza familia yake, hususani binti yake wa miaka miwili.