The relationship is between you and her. The alleged viewpoint of her therapist doesn’t matter. I could give you a compelling argument pro or con to the situation, so what?
Now, if you are beginning to think your gf may be making great points, and your situation truly is not healthy, and want to rethink the holiday and dinner thing, that’s another story.
Also, this dilemma is backing you into a corner as Thanksgiving is coming up. Is it going to be her or them? Can you convince her to come along? Is she forcing you to choose?
How about giving her an engagement ring before the holiday to make her feel secure???
That’s humor just to clarify. Honestly, if you are feeling you need to tape a conversation, it’s never a good sign.