I would email them back stating the facts that you received their message and thank them for emailing you. i would also say that you were taken back by their inability to understand your MI disability that you are going through. I would say you are sorry you bothered her due to her not being able to comprehend what you are going through and that you won't bother her again in the future with it.
Then see how she responds... if she comes back apologizing fine, you still have a friend. This email will educate her unjudgingly that what she said was inappropriate. And if she gets it great. If not then that is the way she will continue to be. Are you just putting up with it for the ability to talk to a human being or are you willing to let it go and find new friends? That is growth and it takes effort but the rewards are great.
I am saying don't give up on people cause we all can say and do things reacting out like her... the above mentioned sent to her might give you the reply to understand just how she feels about things... and then you can go from there.. .tc (((hugs)))