I read an article that discourages T's from sharing any information that might make the client think they are "soulmates" as apparently this can promote a strong idealising transference. So that could be a another reason she didn't share about her interest in art.

Strong boundaries can feel very strict and uncomfortable at times, but remember the reason they are there is to protect both the therapist and the client. It does sound to me that your T is at least professional and safe, which are most definitely good points. She probably felt really awkward as well at the workshop.