How do I deal with my crazy roommate?

My roommate, and best friend for about 10 years now, is going absoluetly batty. I just started a new long distance relationship with a guy I really care about, and all she can seem to do is question and doubt the relationship. Recently she even went as far to ignore us when we came into the room. Her disapproval of the relationship is written all over her face and body language. She asks patronizing questions about the relationship to me, and makes presumptuous assumptions about what his intentions are. IE "He's lying" "He's hungover" or "He only wants a warm bed" None of which are true. She's a hard one to talk to face to face as she always gets defensive, and never believes she is wrong. How do I let her know her negativity is affecting me and making me uncomfortable? Everytime I try to express my distaste for her attitude, (only after she actually acts in such a manner, I never bring it up out of the blue). she gets even more snarky and turns it around on me. I don't know what to do! Calling her a beep isn't exactly appropriate, but that's how she's acting. I'm assuming she's jealous because he's taking time away from her, and she currently does not have a relationship, but i can't exactly tell her that because she'll deny that that's the case. Please help! I don't know what to do, and it's like i'm walking on eggshells in my own house!