I don't know what to say to make it feel better. I've been in a similar situation so what I did was write a letter to this person, make sure you put everything you feel on the letter and then when you're done seal it up and leave it be. It'll help you, I did that and its great! Then when you're done with that, you can try to find things to occupy your mind from these thoughts and slowly each day you'll forget about her and think about her less as each day passes.