It's tricky on how to make yourself less "attractive" (not necessarily physically) to her without alienating others but perhaps finding away to not be so accommodating while introducing her to others who she may latch onto (obviously not someone you like)...might be the one two punch you need.

The other thing is that there are ways to "help" people without being personally involved. Like panic attacks...offer to call an ambulance... When she dramatically falls to the ground in despair... Suggest she gets a therapist or that you could call the ambulance for her so she could get the help she needs in a psych ward....
(I am not saying those things aren't legitimate problems for the vast majority of people but she seems to be a little over the top and it's a little convenient these things happen just when you telling her your boundaries...)

I hate to do things without being straightforward but there are people who will not listen to the words you say if it isn't what they want to hear.