Should I intervene? Parent abusing teenager

[Fairyflaps]

On at 3 occasions now, I've witnessed this woman berating her teenage daughter (15?), in a non-stop tirade of abuse as she walks her to school. The daughter occasionally answers back, but mostly just walks straight ahead and keeps going, while her mother goes on at her about how useless she is. This is loud enough for passers by to hear.
I know teenagers can be infuriating, there must be reasons the mother is walking her daughter to school at an age when most children walk by themselves. But for the daughter to have to have that - I assume every day - in her ear can't be good for her.
Should I do anything? The first time I witnessed it I was shocked, but assumed it was a bad day - we all have them. But I have now seen this on 3 separate occasions when I happened to be walking the dog at the same time they've been going to school. I am half tempted to intervene and say something to the mother, but I'm worried that could make it worse, and make it more cringingly embarrassing for the girl. I know which school she goes to so I could contact them. Or should I just keep out of it?

Bloody hell this sounds awful, and is definitely abuse. It’s difficult to know what to do as you would need to speak to someone and possibly need proof. If you know her name, you could speak to the school and see what they suggest.

you should inform the school, they may have a file

I know the school (my DS used to go there). I don't know the names of the mother or the daughter, but I could draw a picture of them which would probably be enough for the school to recognise them.
I'm certainly not the only one who has witnessed it. There are lots of people in the park at the time, other children walking to school, dog walkers etc. And the mother is so loud. You can hear her from some distance away and she doesn't let up.

what is the mother actually saying? if she’s just having a go at her i probably wouldn’t do anything, maybe the mum is dealing with school refusal and this is the only way to get her there.

it’s a bit hard to have much of an opinion though without having witnessed it directly.

The mother is telling her/ shouting at her how useless she is, what a waste of space, stupid etc. As a one-off this isn't great, but it happens. But multiple times and in a non-stop rant which seems to last most if not all of the journey to school. I think school refusal may be part of what is going on here. The mother certainly seems to resent having to walk her daughter to school and is making sure she knows it.

The person who needs to hear that it’s abuse is the daughter.