I like to know why this roommate's behavior makes you uncomfortable or jealous. It seems to me it is just girls being funny. Now...the roommate could be instigating this, cause she probably noticed it makes you feel uncomfortable, and doing it just to bother you or tease you. So one way to stop this, is to completely ignore it.

On the other hand if this is truly troubling you. You have a problem and should be addressed cause being this jealous (or suspicious) will ruin every single relationship you enter and you'll suffer immensely every time over nothing. You read me well nothing! Fear of losing a loved one can play tricks on you and you imagine things which are not there and blame people for things which never happened or were going to happen. Low self-esteem usually, inexperience.