How to deal with psychotic roommate?

I live with a roommate who is overly passive aggressive, goes above and beyond to make people look bad, always makes asinine, snide remarks, and looks for trivial things to twist into drama in order exercise and justify her imbalance. I am not on the lease, and forced to bite my tongue, and feel powerless. At her age, she is well set in her ways, and talking to her would be futile. What to do?