Help pleaseeeee it's long but I really need advice !?

[anonymous]

So My ex and I have been together for 5 months . Lets say my ex name is John and my friends name is Sarah . So John and I got together officially in September . I started noticing Sarah was acting to flirtious with John . So I asked her about if and she said there was no way she was interested in him . So I asked John if he liked Sarah and he got a little pissed and said "I can't believe you just asked me that" so then I started to have trust in John and felt nothing was going on . So one day I go to Sarah's house and she said "I think I want to add John on Facebook." At first I thought that was a little weird but then I said okay fine . Few minutes later Sarah and I go to another friend house to pick up something and I see John driving and Sarah goes first to his window asking him for his number . I didn't say anything and I regret it . A couple days go by and Sarah is having a birthday party and as soon as John comes in she gives him a kiss on his cheek . I told Sarah I didn't like that . She says he's like a brother to her . But they only knew each other for 1 month ! She was always with us when we spent time together . I felt like she was catching feelings for my ex . Then I found out that John would call Sarah just to see what she was doing that night . He always called her ! Couple months later John moved out of state and we broke up . Sarah keeps mentioning johns name telling me she keeps having dreams about him . And a couple months later I met this guy named greg and I told her about him and she wanted me to invite him to her other birthday party..this is a year later.. I feel like every guy I talk to she wants to have a hold of them as well .. I don't know what is going on ..well I have an idea . But I want everyone's opinion . Do you think this girl is really my friend? Sorry this is super long ..PLEASE HELP ! It still bothers me to this day and I cannot get over the pain I feel .