Problem is, if you only got her 3 weeks ago how do you KNOW that she hasn't missed a feed? I'm not bashing any sellers but you don't KNOW unless you've been there yourself every time. Sometimes snakes, especially BPs need an adjustment period. This can especially be true if your substrate, humidity, temperature and tank layout are different. I would give him a little time and try to keep things as peaceful for her as possible.

Also, try different feeding techniques like turning of the lights or covering her feeding cage with a blanket, things like that.

Has he pooped since you've had her?

Holding a snake is touchy. I guess it depends on the snake, really. If you do hold her, try not to stress her and just be gentle. I wouldn't hold her for too long, though.