I think if she cheated (I don't have any strong opinions on whether she did), that her signal was binary. It makes the most sense given her actions, and inability to explain them.
Buzzer that buzzes when "you have the best hand right now" makes a lot of sense and is easy for a bad player to understand.
It's a coin flip, but she's 55% favorite unless she knows the discarded/dead cards. If she knows them, she has 47% equity which makes her call very profitable given the pot size of 40k.
This is basic "pot odds" or EV calculation, I encourage you to do it.
If she didn't know his exact hand, her play is unspeakably bad. She has virtually zero equity against Garrett's range here. He's holding one of the two or three hands she can beat given his line. Most of his bluffs are crushing her.