I know you've been breeding snakes (from your previous posts) which is why I didn't jump into husbandry issues- I assumed you know that stuff.
Was the mouse you fed her larger than she was previously fed? When we see a malnourished snake, it's only natural to want to feed more food, but remember that dehydration must be considered before the issue of being underweight. When a snake is underweight & dehydrated, they just cannot handle a normal sized meal- but instead need to eat smaller stuff while their GI tract catches up. If that was my snake, I'd feed mouse or small rat fuzzies for a while (weekly intervals) because they're easy to digest. It can take a while to bring a snake back from the edge.
Good luck- I hope that's all it is. You'll need to be patient- & since she threw up the last meal, sadly you'll need to wait longer to feed again to give her digestive enzymes a chance to be replenished now before any more food is given, as paulh pointed out. Repeat regurgitations can kill a snake (due to the dehydration it causes, or also from aspiration into the lung). Be very patient.