I know you just got the snake. She is big and needs to be brought back up to wt. Do you have an age. She's a beauty!

It's really hard to tell from the pic, exactly how big she is but I'm guessing around 3 foot. I'd personally be feeding her adult mice or hopper rats. (does she take f/t's?) I'd feed her 2-4 every 7 days. Some people will tell you to feed her more than that and it's a personal decision but I don't think trying to give her huge amounts of food to bulk her up more quickly is the best for her. She will slowly fill out. You don't want to feed her so much she regurgitates it all back.

She does look like she her sides are concave so I'd also be soaking her in luke warm pedialyte daily for 3-4 days and make very sure she has nice fresh water, every single day. If she is dehydrated she will not tolerate the food as well and can get constipated. Especially since she already looks dehydrated to me.

There are so many great resources on this forum. Any questions you have, someone should be able to help you with.