In my experience 900 grams is pretty small for a 2011 female. That said unless you have an extreme burning need to get her up to breeding weight soon, I would not go the route you are planning. If you want her to put on weight I highly suggest doing everything you can to get her on rats. You will be able to safely give her larger prey items. Who knows, she even may gain weight quicker once she is converted. You need to convince her to convert and give her some tough love. It won't hurt her to not eat for awhile if she is a healthy weight for her size. There are a lot of ways to try to make the conversion and the success rates vary from animal to animal but she needs to be hungry for any of them to succeed.