That is very strange.

I suppose you could confront your T if you find it bothersome.

Personally, I would be quite bothered by her actions/behavior in general. If she's indeed stashing booze, can you smell it in the bathroom? I wouldn't go through her stuff because maybe she's not hiding alcohol at all, but it's okay to sniff around IMO.

Does she smoke? If she does, then maybe she brushes her teeth to get the cigarette stuff out of her mouth and uses mouthwash instead of chewing gum, since it's not not exactly "professional" of her to be chewing gum while she does sessions. (I'm just trying to play devil's advocate.)