You are doing fine. Babies need the extra nutrition since this is the time of their life when they are doing most of their growing. If, however, there comes a point when you notice her getting chubby (generally, you can tell she's put on a little too much weight because you'll see folds in her creases when she bends her body) - anyways, if that happens you can put her on a diet, so to speak.
There are a number of ways to approach this - whichever works the best for you is just fine:
- Begin feeding her smaller prey items (I wouldn't suggest trying to switch to mice or anything other than rats)
- Feed her less often. If she is getting bulky you could begin feeding her every other weekend instead.
- Do both. Feed smaller meals less frequently.
At this point though I wouldn't worry about her getting fat. As long as you aren't power feeding her you should be fine. And remember once she gets older she will begin going on a seasonal fast for roughly 3-6 months a year. Although, mine don't tend to lose too much weight during this time, it is always healthier for them to have enough energy stored in reserves to be able to make it through their fast. Generally, balls don't really overeat. If you are feeding her too much or too often she will slow down or stop eating altogether for a while until she is hungry again.
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Stay United!

I'm still not sure if it's weird that my best friend is a two year old boa named Ronin. He's quiet, non-judgemental and listens... what more could you want?