Hey! Welcome. (Your glider names are so adorable, btw).
It's strange that Watermelon suddenly changed her behavior like that. Is she in heat? Gliders in heat can get really cranky. They go into heat once a month and it lasts three or four days, I believe.
Has anything happened that could have caused her stress? A new pet in the house, family troubles/fights (gliders are very attuned to human stress), a really deep clean of their cage, a change in diet, travels, a lot of people near her cage, new smells in the room that they're in, new sounds? Storms and weather (and moon cycles) can also affect them. Has there been any drastic change in the weather since she started being withdrawn and wary?
Have you changed your shampoo/deodorant/perfume lately? Gliders bond with their humans mainly by sound and smell, not by sight. If you changed your smells, Watermelon might not recognize you and think that you're a completely different person, thus being less trusting of you.
Sorry about all of the questions, I'm just trying to list a bunch of possibilities why she's suddenly wary of you.