She prepared herself for rejection. It made the most logical sense. If the situation was reversed and Ginny was living on the outskirts of Hogsmeade amongst the most loyal and powerful of the Death Eaters and their families, Hermione wouldn't have wanted to offer her the same. Any weapon in an enemy's hand could be the instrument in their death or the death of a loved one. She understood that there would be many within the Resistance who would prefer she remain unarmed. Readying herself for the sting of rejection wasn't the only internal preparation she was making. Her decision was made in that moment. If they told her "no', she was leaving. There would be no point to stay.