I think you have been more than reasonable.
She was extremely disrespectful and as for that boyfriend 🙄.
HIS parents clearly have the measure of them both and weren't going to allow them and their house to be used.
My son was stunned when he moved out at 24 and the penny dropped at how expensive life was and his graduate salary of 40k was competitive in his year.
It is expensive to rent and pay your own bills.
The upside is you are dealing with the real world.
Getting married or moving straight in with someone straight from home is an awful shock if you have been like royalty paying peppercorn rents at home.
My son pays 1,500 a month for a shared apartment including utilities etc.
He loves it, but it is expensive.
If he was living at home I would definitely be taking a fair rent, (would save it quietly as friends do), because the shock of having a large disposable income suddenly taken away from you when you eventually move out, is not doing any young adult a favour.
I know this from friends whose kids were away every other weekend, constant trips, eating out, spending constantly online, whilst paying £50 a week living in an urban setting.
They couldn't believe the reality of living in a shared house at 27/28 and wanted to return home after 6 months.
They all have reasonable salaries.
Its another part of helping them grow up.
I remember eating rice and tinned tomatoes for 🤢 the last 3 days of one month as that was all I had in the cupboard having over spent, age 21.
I learnt the importance of budgeting quickly enough and I made sure I had more food bought for the end of the month next time!
The OP is doing her child a favour by getting real.