Friend is so flakey - need advice

Hi <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">Eve</a>, I want to know what you would do in this situation:

I have a friend who is such a flake. She has always been late to things for years but in the last year it has become a joke. She is often visiting her boyfriend so cannot attend our plans, but when she is in the same city as us she always cancels at the last minute, even birthday meals/drinks/days out. Or she changes plans to better suit herself before inevitably dropping out or leaving early. She knows that things have been booked to include her and yet still flakes. She recently became annoyed that she hadnt been invited to a meal (by mistake) yet hasn't attended a single plan as planned since then - so she would not have gone anyway!

She does have chronic health problems however she manages to attend plans with her family, boyfriend and other friends without an issue, thus tiring herself out so she is 'dying' too much to come to ours. For this reason I feel very guilty if I think about cutting her off, because it could easily look like I did it because of her health problems.

What would you go?