My girlfriend's flatmate called her a slut?

girlfriend is hanging out with her best friend (female) who's come to work in the same town.

Which is great, because she's having a really bad time with her flatmate.

She sent me a text earlier saying that her flatmate pretty much called her a slut and is asking the landlord to kick her out of the flat.

He says she brings different guys around all the time:

Me, her gay friend and a best friend whom I met last weekend and he's already in a relationship anyway and is a nice bloke.

I'm listening to her, I'm trying to show empathy as best as I can. Not offering advice or anything, but I'm almost wanting to go over to her flat for a word with him.

What can I do?

My girlfriend's flatmate called her a slut?
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