At this point, you may actually want to tell her about the bipolar. I'm assuming you're in the US, correct? Bipolar disorder is a covered disability under the Americans with Disabilities Act. If she does tell you tough s***, you can report her. I'm not sure what is within her power to do, as far as giving you extensions on your assignments and such, but she can't just ignore it. She may just direct you to the school's disability office, so you may want to start with them. Not sure how your school's system works. But this is one case where having a diagnosed bipolar disorder is actually to your advantage and allows you some Federal protection.