It's hard to move on from things like this and from things we are used to. Some things are hard to let go of. Try to think of it as a period of grief, hopefully it will start to get easier. It's ok to be sad about it though, but don't let it take over completely. Besides, when someone leaves it makes room for someone who might be better for you. It sounds like you weren't appreciated anymore and you deserve to be appreciated, I'm sure you're a great friend and it is her loss. I know it's east to say all this but time can be a healer and I hope it will be. I would say try phase out looking at her online stuff, I know it's tempting but if it's gonna hurt it's not worth it. Do you have other things to fill the time you usually spent with her? Maybe that would help. I've lost friends recently too so I know how it feels. I used to get really down over it too but if they want to leave then they're not worth us feeling that way.