How likely is that a second episode will happen?

The statistic I have seen is that 50% of persons with SZ diagnosis and 40% of persons with BP diagnosis have anosognosia, or “lack of insight” (their brain tells them that they are fine and NOT sick) either completely or to some degree. We cannot MAKE the person do anything but we CAN communicate with that person in a way that may lead to the person doing what WE want not because they are sick, but for a reason that is meaningful to him/her. We may also have things that we can use as leverage to help the person comply with medication, treatment, therapy, or other situations as well. Marijuana does not CAUSE SZ but it can trigger it or make it worse. In regard to the extent and frequency of illness, each person is different. However, if she really had SZ, I would have expected additional breaks. Since she was only hospitalized once, it is possibly she has something else or multiple things going on (like bi-polar as you suggest), or PTSD.