I adopted 2 female dumbo rats a week ago. They are just over 5 weeks old. They are in a three tier wire cage with food bowl, water bottle, house and rat safe toys. One of them was skittish at first but has slowly opened up and now is playfull, happy to see me and likes to be held. The other is terrified. I can't get her to come out of the house. She won't take treats from me and does not want to be touched. I've been taking it slow with her and waiting for her to come to me, but after a week there's been no improvement. I feel bad that she's so scared. Do you have any advice on how to make her more comfortable?