Assisted living is not a nursing home. Essentially, around here, it is a serviced apartment with meals, and some care options (medication monitoring, dressing assistance) available as needed. People usually move to these in anticipation of needing increasing help. The apartments tend to be quite small and there are many common areas, activities, and transportation options available, and usually a nursing home facility is attached or affiliated when or if someone needs it. It is rather like the old-style "apartment hotels" that I always thought were a great idea.
It did just occur to me that perhaps Aunt wanted to limit the gathering to "family including recognized social units" because she wanted to talk about giving her china, silver, crystal, books, piano, furniture, etc., away, because she won't have room for very much at all after she moves. That is not the kind of conversation one might have with random strangers, or even with friends -- unless they are to be included in the distribution -- around. No piano for Larry, and I can quite understand Aunt being fried at having her plans derailed, though Aunt could have closed that door, as could Larry. As soon as she know the score, GF could have said, "Ms. Aunt, I am so sorry. Larry didn't say this was a sit down dinner with limited space! Let me call a cab, and I am gone. I'd like to meet you another time, though." This gives Aunt the chance to say, "No, Martha (GF). Not your fault, and we're happy to meet you. Please do stay, we'll just set another place," or "Thank you for understanding, Martha, I look forward to seeing you another time, after I have moved." And then called that cab for Martha, or point Martha to the phone. If she froze, though, which I can understand, and Larry kept whispering "it's fINE" and cabs aren't readily available in the area, she did the best she could. She sounds kind of clueless, though. She moved in with this clown? Sigh.