Button, this really does seem to have bothered you... You didn't go out looking for dirt on your T, but never-the-less you have heard things about her that don't sit well with you. If you don't bring it up and discuss it now - so she can tell you her side and you can hopefully get past it - my fear is that it will come up again later, maybe sometime when you get mad at her for something or are resisting the work for whatever reason. You'll maybe have thoughts like 'well why should I listen to you? I know what you did...' etc.

I think holding something back in a therapy relationship can really affect the work you're doing - and like someone wrote earlier in the thread, it's going to be the 'elephant in the room'. Rather than have the risk of a rupture over this down the road when you've invested so much more into the relationship, it really could be better to get the discussion out of the way now, then hopefully you can move past it and work with her - really work with her and trust her, without having nagging thoughts about her in the back of your mind.