Only the Strong Survive...
I need some advice, please…

I’m supposed to be moving in with two of my friends in the summer. It was gonna be just the three of us but two things are worrying me:
1) I don’t want to leave my current flat mate with nowhere to live or no one to live with.
2) One of my friends has asked if one of her friends, who I really don’t like and don’t get on with, can live with us too.
I don’t want to upset anyone or make anyone unnecessarily uncomfortable so what do I do?