Just a note but hormonal birth control "tricks" the body into believing it's pregnant and so it doesn't ovulate. The problem with that is it comes with a huge host of mental health issues, like depression, manic behavior, over the top anger, etc. In recent surveys they've found that women who took it had extremely high chances of developing depression.
For someone who has mental health issues already her going on hormonal birth control would probably make things much, much MUCH worse. She's a bit smart to want to avoid that.