It sounds like every time she does something like that, you just sit back and let it happen. How the hell is she supposed to know it hurts you if you don't TELL her?? Telling her one time, probably YEARS ago, that you have a health condition isn't going to do sh*t if you haven't mentioned it since. If I were her I would assume you got better or something.
If you don't talk to her, it's not her fault that you don't like her greetings.
Your friend sounds like an absolutely terrible friend, if she even truly is your friend.
She may not realise the seriousness and severity of your condition, so you should probably explain it to her again. If she still doesn't listen, you may want to consider not being friends with her anymore. You don't need to be friends with someone who treats you so terribly despite knowing how much it hurts.
I know "get new friends" is a lot easier said than done, but you really should try making friends with some people who will take your medical condition into consideration and treat you better than your current best friend.
Good luck.
Bitch. she is NO friend. A friend would be like how are you today. can i help with anything? Not be like, heyyyyyyy imma jump on you.. no.