Unfortunately, we don't have a lot of context here, which is important, but if this lady has serious mental problems, then this video saddens me on a lot of levels. First, because she's likely dealing with some serious demons in her head and, as it's been pointed out, probably isn't getting any decent help, meaning this is a normal day in her life. That fucking sucks. Secondly, we have a group of people stoking the fire and making fun, causing the lady to have a violent response. That is not OK! Call the cops and keep an eye on her, but don't film, make jokes, antagonize, and put it on Twitter for some cheap fucking likes.
I'm really sorry that you're having to go through this, but you're also awesome for your compassion. My mom had dementia and passed a few years ago, but had some of the same types of behavior you noted above. Being there, feeling helpless, and watching everything just slowly slip away it not something I'd wish any one to experience. It's a real shitty way to go.