My Cham has done this several different times, opens her mouth like she yawning throat puffed out and like twitches. Her butt end twitches and mouth opens wider. Does this only a few seconds What’s wrong with her?
i second thisIt sounds like she is just getting defensive. My male jacksons xantholophus does this--especially when I start rearranging his cage. They do the twitching/jolting movements to show their annoyance at you.
However, if your female is getting too hot and is gaping for long periods of time, you may notice that she has lighter colors as well, trying to cool off. In this case, lower the temps. If she is only gaping when you approach the cage, then I wouldn't lower the temp at all--and you are keeping it at 80F so that's good.
I would try to leave her cage alone as much as possible. If you need to redecorate, do it all at once and then leave the cage alone. Once you leave her cage alone for a while (a week or two or three), and only approach to feed her, she will stop gaping and twitching at you.