OP the problem you’re facing on here is that you have given ZERO indication of where in the country you are and average house prices.
A 4 bed in EAST EAST EAST London (basically essex) would cost you between £450K to £600K (Yes, in essex), whereas the same 4 bed in Sunderland will probably be around £120K to £160K.
The only thing that would make sense here is that you’re in the mid-north and avg property prices are very low needing only a £100K or so mortgage.
Anything else and you’re stuck in the past.
We have a whole generation right now that think that 0.5% Band of England base rates and therefore 1.5% interest rates on mortgages are normal and the norm (anyone 30ish or below really right now), please note those were artificially engineered by the Bank of England.
That’s not normal.
So payments of £500 a month are ridiculous for the majority of people taking out a mortgage on year 1-3 on a standard 30yr mortgage (yes, also most people take out 30-35yr mortgage as the norm as the only way to make repayments work out).
Lastly, your daughter is an adult and she can make her own decisions and personally I don’t really think you should be interfering much about this given that you don’t even know what her salary actually is?
You also don’t know for certain whether her ex was even contributing to the mortgage payments. I assume he was contributing to other costs, but still a relatively large unknown.
If you really want to “interfere” then you can simply tell her that you’re concerned for her as you don’t think that you and dad could help her IF hard times were to come by.
You then leave it at that. Don’t mention it again.
I also personally think that possibly she is taking a bit of time to process the breakup and re-learn life differently.
House moves are… a LOT. They also cost, a lot.
She also had this house BEFORE him, so why shouldn’t she continue to enjoy it?
I find this rather bizarre.