If you talk to your acquaintance about this, you might suggest, if she wants to get back on an even keel to take and give the tape to her T? At least not keeping the tape would help a little in the equation of taping without permission in the first place.

I don't know that the T will be "worried" or anything were she to learn she'd been taped; I doubt she feels her words can be "used against her" or anything, it's mostly just a trust/politeness issue. I would think she'd be angry (which might be misunderstood) but I think it's more the surprise and unexpectedness that is hurtful.

I know lots of people who save PM's and e-mails, etc. and the people sending them don't realize it nor do the people who save such things think anything about saving them but it's a similar issue. It's not being given the opportunity to decide how you feel about the other person "keeping" your words that makes the differerce, not necessarily the words themselves.