How long?

That's a lot of difficult things to deal with in just one year. I've definitely been in a similar place. First of all, there is no time limit for grieving, or "getting over" something, it takes time. If you can learn some coping strategies, I think that could help you to process your feelings a little more efficiently.
I know it can be difficult to resist someone who you've been close to before, especially after losing someone like your grandmother who's probably given you a lot of comfort. I'm sure all you want is to turn to your friend for comfort. But if she's betrayed you in the past, it might not be safe to let her in again just yet. You didn't really give any details about the betrayal, but if this was truly a cold hearted betrayal then this person is a liability. They will hurt you again if they are given the chance. The state of vulnerability you're in right now makes it really easy for someone like that to get close enough to hurt you. I don't mean to tell you to blow her off, I obviously don't know all the details, but I think you should be very wary.

Life can be very difficult at times. The trouble is that as much as we know things will get better we also know they will get worse again too. So what can we do about this uncontrollable roller coaster? I think it was Dr. Phil (who occasionally has some good insights) who said, "It's not whether or not people will let you down, they will. It's whether or not you can handle it when they do."The biggest favor you can do for yourself is to equip yourself with the skills required to negotiate life's ups and downs without falling to pieces during the downs.

I struggle with the idea of time and being over certain things too. But honestly the pain will never really go away. I dont think that anyone can ever get 'over' something that really hurt them. You can move on and not dwell on it or let it affect your life, but you will always remember. The best thing to do is to learn the lesson that it was meant to teach you and to not focus on those negative things. I know I still get bad feelings when I think of the times I was heartbroken but thats only because it hurt and it will always hurt.. I just dont dwell on them anymore.

You may never get over it. Like the others have said you need to focus on positive things. Don't feel like its bad to have down days, or days when your angry, thats all normal. Keeping yourself level headed and thinking about the good things will get you through it. Talk to people about whats happening in your life, you will be amazed how many friends or family members can brighten up a gloomy day. Find things in your life that you love doing, make you smile, make you happy. So when your feeling like you need some time out you can always turn to these things and you will feel better!