I lost a few very close friends in a short time but I lost one of my very best friends a few years back. We had known each other our whole lives cause our brothers were best friends and they met when they were 3 and we are 3 years younger then our brothers. We went to school together and were in the same class for 11 years. We were only 16 when he passed away suddenly from meningitis. It's like he was totally fine besides feeling like he had a little bug so he went to bed early and the next morning it was to late.
It takes time but in time the pain does ease and instead of crying every time you think of something funny she did you learn to laugh. I can honestly say you will probably never go a day with out remembering your best friend but with time you will find it easier to think of her everyday. Hope this helped some.
Feel free to PM me anytime. I hope you can fine peace and comfort soon.