My sister laughs when she is nervous. So the previous post is accurate in that laughter can be a sign of false bravo or some other emotion. Also, the laughter says more about the mother rather than about you. She didn't know you. She just laughed for some reason. She may have been so desperate for a drink from having to go without during the pregnancy that her addiction might have made her act stupid. In other words, you will probably never know what was going through her head unless you can ask her. So, I'd try to show yourself and fight like hell to convince your brain that your T won't laugh at you.
I keep telling my T that she is not allowed to leave for a while. She keeps telling me that she has too many clients to leave any time soon. But, I keep fantasizing about her walking out of my life. Ironically, I had this same fantasy a week before my old T changed offices to an office that I can't get to on the bus. Then my psychiatrist left. So I know what you mean when you say that you know the thought is unfounded. Even when it is unfounded, it is still hard to get it out of your head.