To be perfectly honest, she wasn't slammed and I wouldn't call her elderly. She's in her 50s from the look of her. The dumbass guy was trying to pick her up to carry her to the pool and throw her in but he slipped, so both of them fell. He picked her back up and threw her/jumped in the pool with her. It's not as big as deal as it sounds in my opinion.
The black kids were extremely disrespectful to her and shouldn't have threw her in, though. On the other hand, the white woman had no sense going over to party full of black teenagers to tell them to turn down the music with all of the BLM crap going on and things being more racially charged than ever. She should have just called the cops to deal with trying to get them to turn down the music.