She sounds fine to me. The squirmy part is a little weird to me but, I don't think it's a problem. Ball pythons are lazy animals. They hardly move. They are also prone and known for going off feed for up to months. Also long as she doesn't look physically skinnier, I think you're fine. I would take her out of a tank though. She might be stressed. I recommend putting her in an appropriately sized tub. Someone else can help you with the size, sorry. Good luck with your new pet!

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