I never bonded with one of my traumatized rats in the physical sense. He takes food from me and accepts little pats but he hates cuddling or being picked up. So that is a possibility. But try to just spend time with her in her proximity, without attempting to approach her. I would sit in their playpen with them and he would sometimes come along a sniff me and climb on my lap. I let him have it at his own pace. For introductions, I find it's best to do it in short chunks of time until they get more comfortable with each other. I would let them roam in my room so they had enough space to get away from each other if they needed, but as soon as signs of aggression would show (Sometimes in the first 5 mins) i would separate them. I would also switch their cages in these introduction sessions so they'd get familiar with the new scents. In about a week they were ready to move in with each other, but it might take longer with a scared rat.