Daughter split up with partner

How does the daughter stand. Shes just split up with her boyfriend after living together for 13 months.
Situation:
Mortgage in both names
Both helping with bills. He paid mortgage while she other bills

He says as she left he wants all money off her for 13 months mortgage.

He's hidden all paperwork relating to bills etc

She's living with us at moment he keeps making threats to take her to the cleaners by text all saved for evidence.

He now got his brother living with him. Can we get him out.

He wants the key off her for the flat as she left. No way though.

What should I do?

What does he want aside from the key? What is he attempting to acheive?

If the mortgage is in her name as well as his then she needs to sort that out pronto.

I don't see that he can "take her to the cleaners" either. They aren't married and have been in a relatively short relationship. She should hang onto the key as it is her property too, and ask what he intends to do about taking over the whole mortgage and having the deeds transferred to his name only - or selling it and sharing the proceeds with her.