friends who act like SOs?!

[Beluga23]

Has anyone else had friends who acted more like significant others than an actual friend? I've never been in this situation before her... and the worst part was, this friend was someone who felt that I was responsible for all of her emotions (basically, she wanted me to be there for her every need.) I understand that we should be supportive as friends, but... there IS a line, isn't there? Finally, after years of fighting and her guilt-tripping me (and forever telling me that I'm a horrible friend, a drama queen, etc etc.) I just decided to tell her that I couldn't be friends anymore. This felt way more like a breakup than anything. How does that even make sense?