Girl's Behavior

What to do when you're flatmate is a slut?

There are 3 of us liveing in a 2 bedroom. Me (male) and two girls shareing the second room. They where friends before I knew either of them and I have been friends with the problem flatmate far longer only met the good flatmate when they moved in. Now I can deal with problem flatmate not cleaning or washing excetra since it still gets done. The problem is that good flatmate is not very dominant in the relationship, when problem flatmate wants to bring a root over then good flatmate goes stays elsewhere. Now I dont want to slut shame but she had a guy over yesterday and last night now its 10:30am and a third one is here and Im not supposed to mention the others its not respectful anymore. I dont want to drive a wedge between friends but I am thinking I would prefer just one flatmate. Im the landlord and pay power/water good flatmate pays for fiber internet plus contribute towards food and stuff and also does her share of chores. I dont see this as fair but dont know how to deal with it nicely? I would happily let good flatmate have the whole room free so its not like they need to split rent there is none and what expensise there are I pay anyway. I just dont know how to tell the one who is suppose to be my good long time friend that it would work if she just stopped fucking people all the time.

What to do when you're flatmate is a slut?
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