I have bipolar II. I was officially diagnosed about 2 years ago. I met my husband about 4 years ago. I knew something was wrong with me but I didn't know what. So I did not tell him either. But I didn't not tell him to deceive him, I just didn't understand what was wrong. I just thought sometimes I was seriously moody. I also have panic attacks and OCD which he knew about, but that is very minor compared to what I go through with the bipolar.
Maybe your ex didn't realize how bad she really was. It's very confusing and scary for the person who is feeling it. As I'm sure it was for you seeing what she went through.
I was handling it pretty well up until the 2 or 3 years ago when I was diagnosed. Now my emotions are a roller coaster. I tried 3 or 4 different meds and nothing is helping. So now I stopped taking them all.
I don't think you should talk to her, unless you realize what your getting yourself into and are ready to help and support her. Otherwise I think you both will end up with more hurt feelings. It takes a long time to find the right med that works for each individual.
If I knew then what I know now, I would have just walked away from my husband because I feel horrible for putting him through what I do. I think he would be much better off, although he would never leave now. We have the most amazing relationship when I'm feeling "normal" but that only lasts for a while, then I get very depressed and angry and make both of us miserable. Then it starts all over again. It's like I'm a different person every other week.
Think long & hard before you have contact with her again. Unless you sure you want to be with her it's unfair to confuse her more.
Hang in there. I hope everything works out.