How do you know that she is flirting just with you? She may be that way with everyone. "flirts very strongly" what does that mean? Can you give examples?

You feel vulnerable and the attention feels so good, but this situation is a time bomb waiting to go off.

Will it feel so good when you lose the apartment, the friends and her attention?

This may be part of a larger plan to get you out and them into the master bedroom. Just sayin.

Who's name is on the lease, btw?

If you are afraid of being alone with her then you'd better make some changes. Your roommate should also be made aware of this situation.