So difficult. Agree you need to meet elsewhere - but also she needs support with her parenting. Her son may have additional needs, or not - but it's very tricky to tell people how to parent.
No advice really - but reminds me of someone I knew. She was a friend of a friend but we used to meet up at the same toddler groups and activities over the years, so I was on chatting terms, and saw a lot of her son's behaviour first hand, from baby up to about aged 9.
She had various other issues including health related, and was a single Mum with no Dad in the picture. It was never going to be easy, but she had firm views about parenting such as never saying 'no' and co-dependent behaviours which I gather escalated as time went by. Our mutual friend had to drop the friendship due to the boy's behaviour, and violence towards his mother, and felt awful but she couldn't let her own son be party to that. I think the boy may have been diagnosed with Aspergers later on, but he probably wasn't helped by mixed messages and parenting issues that I can't expand on without maybe being identifiable. The last time I saw them was at a school holiday group where the child left the building and wandered back home - aged about 8 or 9, causing panic.
They moved away for a fresh start, but sadly I heard the child was taken into care a few years later as the mother couldn't cope. Heartbreaking for everyone involved.
I suppose what I'm saying is that it may be poor parenting and it may be additional needs, or both - but these things can be very complex! If she is a good friend, please try to be there for her (although not in your house)!