In desperate need of some girl advice!

So i have been having alot of problems with one of my best friends lately. Shes really my only close friend that is a girl (i'm a guy and i hangout with alot of guys) and we go back pretty far so i guess i'll explain things in depth.

I have known this girl for about 6-7 years and we dated briefly when i first met her. We have been friends since then but sort of on and off and not that close. I hadnt really talked to her or seen her in a few years until last summer and we started hanging out again. We started hanging out alot over the summer and got really close really fast. I wasnt really attracted to her more than friends at that point but for the first time in the 6 years ive known her i felt like i actually got to know her and her personanality. We became best friends within like 3 weeks and she called me everyday and we would hangout everyday. Things were so different with her than any other girl ive known. It didnt matter what we did we always had a great time together even if it was just sitting at home and watching a movie. We have the same group of core friends and none of them know her like i do. She is really shy but with me she acts totally different and is herself, we are so comfortable around eachother. After about a month that summer i realized i had fallen in love with her. Well after an amazing summer with her she went back to school and we were apart all year (she goes to school 3 hours away). I ended up telling her how i felt but not to the full extent and really not how i wanted to. Things were a little weird for a while but we talked pretty much everyday she was gone during the year and eventually things went back to normal with us. I was so excited to spend this summer with her but about a week before she came home for summer she started seeing someone at school. So that brings me to here. Shes my best friend and i really dont want to lose her. Things have gotten harder than ever with her dating someone, it has really taken away from our relationship. I always felt we were as close as friends could get without dating. I dont know really how to deal with the situation. I miss how close we were before she started seeing this guy and im so in love with her i think she should be with me. As happy as we have been being such close friends i think she should take a chance and be with me. I guess it just kills me because we cant be how we used to be as long as shes with him. What do i do in this situation? I dont know if i could deal with losing such an important person in my life but i am at a point where i dont know if we can be friends if shes with him.

You are not losing her if you just let her date that other guy. She will still be your friend.
Does she like this guy a lot? What did she tell you back when you told her how you feel about her?

Maybe you could tell her how you feel again. Tell her that you dont want to end your friendship if she doesnt feel the same way. But if she really likes the other guy, let her be happy. However you never know what the future will bring.