I didn't get any insinuation, I didn't think the mom was dressed especially provocatively either, and it never occurred to me that anyone would think anything sexual about that moment until I read what you wrote.
I took the mother saying, "Let's have some fun," as a response to the fact that the daughter was basically saying, "No on wants to hang out with me and do fun stuff, Mc and older sister do stuff together all the time, and I'm just left out," so the mom was like, okay, let's do something fun then and take your mind off it. Like dance and get a little drunk before going home.
But like I said, if you see innuendo there then not much to say, I just think most people didn't but maybe I'm wrong and I'm the one in the minority.
