why does my ex expect me to allways be there for her?

[Antoine]

Me and my ex girlfriend broke up november 14th yet through everything we have remained friends. a few days ago I had made plans to go hang out with a female friend of mine to see if things could work out well to make a long story short yesterday I was suppose to meet up with my female friend and my ex called me cause she wanted to come to my place to spend time with my cousin her new boyfriend he cant go visit her cause her family doesnt like him. I politely told her that she cannot just drop things in my lap all of the sudden cause i already made plans well when she found out i was going out to meet a potential partner she got irate yelling at me and constantly texting me so I gave in and came back home cause I knew if I stayed out, she would keep texting/calling my phone and it would ruin my date. well the girl i was suppose to meet up with told me not to call her again and deleted me from facebook beacuse of this. even though I called her and told her why I couldnt make it cause my ex was irate about getting her way. my questions are as follows....
Why does my ex girlfriend always expect me to be there for her?
Is my ex just using our friendship to see her new boyfriend and have sex in my house?
why does my ex dress provocativly for him but she never dressed like that when her and I were together?
I really do still love my ex, how do I show her I can be a better person?