Thank you for the ideas.
Just to elaborate on the other student's other behaviours - after the slobberysounding gum-chewing, then she starts biting her fingernails loudly so that
every breking piece is loudly audible. Then she starts making mouth clacking sounds (that seem to have something to do with her lip jewellery). And at the end of the class, she states to me abouit the noisy drilling from out in the hallway that's bothering her. Actually, in other classes - students have been told "no eating" in the room, plus no cell phones. Maybe there's a workable solution through this?