If the first weight was a "full" weight then it is possible the weight loss is just due to waste elimination. Remember these snakes can eat 10% or more of their body weight in one meal, then go several meals before pooping. Plus they pee a lot at one time, and water is heavy. So that adds up to a lot of weight loss just from one big pee/poo.

If the snake continues to lose weight and/or show other signs of illness, then I'd start to worry. Until then, I'd just assume it is a feeding strike related to the stress of adjusting to her new home. Do everything you can to make sure her temps & humidity are spot on, she has adequate hides, etc., and then just wait it out. Adding stress by assist feeding her doesn't seem like a good idea.