Is my Ex girlfriend in on this? and why??!!?

met my ex's friend a long time ago. Anyway she gets on msn and starts saying shes thinking of me and that she wants me and she's liked me for a long time now and thati should go to her house. And i didn't believe her at first and still dont completely , and she said that my ex and her are not friends anymore because they got into a huge fight because it was over me partly and they were ok again until my ex saw her Texting me then they parted ways (this is what i'm being told) anyway i ask this girl out on a date kind of and she said not happening? But then the next day at night she says "call me!" and i got a text from her from a guy that goes to her school and it said " this is steve, she's mine" Then i asked her what that was all about and she said i'm a threat to him and he's kinda with my ex anyway. So this girl tried calling my cell 4 times and i didnt answer and i told her to call my house and she did this morning and she tried to make it sound like i wanted her to call but i put her story straight and she goes"oohh:(" then she wanted me to go to her house again and i said no and she kept asking questions . Like if i miss my ex and i told her "how can i miss someone i dont even think of" and she asked if i had a girlfriend and stuff like that then i told her to come to my house! instead and she says i dont know where you live! and she kept calling me y ETC so is my ex girlfriend in on this and also after i got off the phone with her i left to go out and i came home and on the call display my ex called 10 minutes after i got off the phone with the one that apperently likes me...and i sent them both a text asking why they called my house...now what?