Roommate advice?

CondraSheera • Married to my best friend. Using this app to track my cycles, not TTC.
My roommate and I get along extremely well and can share almost everything no problem. We never fight and have become best friends. Lately though, her moodiness has really been getting on my nerves. 
​I'm an extremely laid back kind of person. I don't stress out or react strongly to rough situations. She on the other hand has adopted a very pessimistic view of life. A guy she was interested in and has been talking to only a few weeks actually has a gf and isn't interested in dating, but wants to be friends. My roommate wants to give up on life and literally pulls on her hair, screams randomly in the house, and asks the same questions over the same issues constantly. On top of that she constantly stresses over every other tiny thing such as moldy bread or a missed appointment. I've been in her shoes and I try to support her but she refuses my advice. She insists I have a perfect relationship and could never understand her. 
​Its getting discouraging since I try to be optimistic about even the worst situations in my own life. Advice?