How resilient are ferrets to high falls?
If something did happen to your ferret, I’m sure you would be noticing signs of something being wrong by now. As for this window, do something so that she won’t be able to push it open (if she really can push it open)! Not only do you have to worry about her injuring herself from the fall, but you should also be worried about losing her. Ferrets are very dependent on us humans and if she would run away, you most likely won’t see her again – they cannot survive in the wild. Please do something about that window (and check the rest of your house to make sure it’s 100% ferret-proofed as well) and get her to a vet if you’re really worried that something could be wrong.