I cannot sleep ! iseeher?

So the problem is that when ever I try to go to sleep at night this image of a girl flashes and I unintentionally start thinking and fantasizing about her (not in a sexual way) , the problem is that this girl 'candy' is engaged to some other guy and loves him a lot. And I feel getting in between someones relation wouldn't be nice for either of us do I walked away and she too didn't knew I had feelings for her . Now I tried everything from jerking of her name as my friends advise to keep myself occupied which my consular said and yes it does help all day but what about night - I cannot sleep . Now I tried counting and and tried thinking about other things but this girl keeps visiting and haunts in my dreams , dreams like we are on a date , or I am saving her for someone, or something like we've been married all weird which isn't possible . What do I do I really don't want sex from her I just like looking at her and ever since she got engaged I just went away from her fearing I could get hurt but the problem now is I cannot sleep. And yes I am dating other girls and this is not a help.