You don't even know if you have Bipolar or not.. If your friend is all worried she may "catch it" .... Tell her to "google" bipolar and read the definition. Teenage hormones are all over the place and apparently shes very impressionable. Maybe just stop talking to her about your moods and how you feel day to day???.. You worry about you and let her worry about her and be friends on a happier set of topics.

Just my opinion of course.

Good Luck