It is kinda weird what happens to the glider you loved and accepted once they become bonded. I am going to assume you aren't bonded yet and Sassy is just scared so she compensates by being tough. Make sure when she gets treats that she sees you holding it and then she has to come to you to get it, this will strengthen trust and make her feel more comfortable in her new environment, try some gliding exercises after that too. When she is high up hold out and show her the treat then pull it back to your chest, if she trusts you she will glide to your chest or find a way to get to it lol, if she doesn't keep trying.