Regular posted but name changed. I’m growing increasingly worried about my neighbour, she’s a young girl in her early 20s I would say. When she first moved in about 3 years ago she lived with her then boyfriend. The opposite side of our street there was a house that 4 people lived in, a couple and two men house sharing. This is relevant. About a year ago, she broke up with her boyfriend saying they were arguing a lot and was fed up. Fine. I started to see her coming out of the house opposite, she then told me she was dating one of the guys. This was days after breaking up with her boyfriend, fine, her choice. Anyway, within about a week he started to have sleepovers at hers etc, I then saw her about a week later and she said his housemates were all moving out of their house as covid had meant changes with their job and they were moving to the next town to follow work, and that he was ‘looking for somewhere to live’ as his job hadn’t been affected by the pandemic. I said be careful that you don’t end up with a cock lodger basically. She laughed and said her mum had said the same.
Anyway, from that day.. he never left. Now I don’t mean this to be nasty, 
I’m explaining this so you can understand the situation. She is nice girl, but she is quite large, often smells unwashed, greasy hair, looks like she has rolled out of bed kind of look. Her ex had a similar look. New boyfriend is older than her, tanned, slim and is attractive to look at ( not to me as he gives me the creeps but) I feel like she thinks he is a god and she has struck gold. She mentioned before the stares they get when they go out. To me it is clearly obvious he is using her for accommodation. I feel awful saying that, but I think you would all the same if you seen them. She told me before he often shows her pictures of his beautiful ex girlfriend from his home country and that it makes her feel sad and jelous, I asked well why is he showing you anyway? She said to remind me what kind of woman he can get if he likes, she is laughing when she says this??
For about the last 6 months, I hear awful shouting coming from the house. Considering she said her and her ex argued a lot, I never heard a peep. This is a lot of shouting. They sit drinking together ( she often says she’s hungover when we say hello in the morning) and it always seems to turn sour. She often shouts back I’m not saying she is woman who is too scared to argue back but it is always saying things like ‘ stop threatening to leave me all the time’ and pleading. One day the noise was so loud I text her asking if everything was ok, she replied what do you mean??? I said there was alot of shouting I didn’t know if you needed any help or the police, she replied ‘couples can have an argument you know, mind your business’. I replied ‘no worries, it was that loud and banging I was worried it was an intruder’. I took the snapping at me on the chin as I was happy knowing she knows I can hear should she ever need me.
Last week I was putting water and oil in my car, they pulled up on their drive. he knew I was there. He had parked close to the wall so she didn’t have a large space to get out, he had got out and was asking if I needed help (such a gent-not!) and she wound the window down and said can you pull the car back I can’t get out. He said ‘omg can you really not get out that space you big piggy, I’m not moving it you should lose some weight if you want to get out’ laughing at me as if he was showing off, she smiled as if it was funny, it wasn’t, I said your a better woman than me I would kill someone if they said that to me, she proceeded to climb to the driver side and get out, he could have moved the car but I feel he wanted to humiliate her.
There has been so many things like this I have overheard, on top of the shouting and banging around. which leads me to my question- what do I do??? I am a single woman living with my children so I do not want to anger him obviously, and she has told me to mind my own business before. If I called the police it is very obvious it is me ( no other houses would be able to hear) which is fine if she accepts the help but if she denies it. Her mum used to visit often and now I honestly can not remember the last time I saw her there, to even try have a word with her.
I’m worried where this is heading, or am I being dramatic and should I mind my own business like she said? I’ve just been woken up again by shouting, the Doors slamming and her sobbing in the garden and his muttering. I feel like she lets him get away with this because she thinks he is the best looking guy she can get, which even if it’s true surely being with someone KIND and not a bully is better 
Sorry this is so long I just didn’t want to drip feed, what would you do honestly?