People without bipolar saying they’re ‘so bipolar’ etc

Something that makes me really upset is when people say they are bipolar or any mental disability for that matter when they’re not (I’m so OCD, etc). And this time it hurt even more, my best friend showed me a shirt she ordered for herself and it said “all aboard the bipolar express”. She said she thought of me… idk it really hurt my feelings. I wanted to say something but I can be kind of timid that way. I don’t know if I should or not. Does anyone have any advice as to if or how I should say something to her? Anyone else have experience with this that they want to share?

EDIT: I talked to her and she was really understanding. She said she would never want to do anything to hurt me and that I should always be honest with her. She also said she liked the wording of the shirt more than the sentiment I guess, i told her it is a pretty good pun lol