What Causes Delayed Periods With Blood Filled Mucus Discharge?

My girlfriend is 2 days late for her period, has had some sort of stringy mucus with spots of brown (presumably blood), was achy all over her body about 1 or 2 days before her period started and now her ovaries hurt. I'm confused. She also suffers from ovarian cysts, but hasn't complained of ovarian pain for some time. Is she pregnant?