This is all kind of mad.

How sure are we the dude is LC's partner and the pdoc? Or is that just a maybe?

He could be anyone. Friend of the family? Her child's father?

I have lots of sympathy for her showing up in 'your' space. Once I was working at a very high profile event (big, exciting and stressful and had talked about it a fair amount in my sessions coming up to it) and I got a text from my ex T saying she really wanted to come to the event, just to let me know. That was weird enough, and hurt me in a strange way because we didn't actually see one another - she just texted again when she left saying how great it was and thank you for my part in it. I really would not have liked the sudden wtf moment of running into her by surprise when it was 'my' thing.

Growli, you really do need to start having the conversations around the fact that she is not your mum. With yourself, with us here on the boards if that helps, and with a trauma T when you finally get one. The brick wall refusal to even begin to start looking at the facts isn't going to serve you. Nobody's saying you have to be cool with it and cheerful about it. But you really do need to start talking about the reality of it.