Of course dear all of us have our fair share of loosing someone we love so dearly. It is really very very hard to cope up. I know time heals all wounds. Just a word of advice, try focusing on her life when she was still alive, celebrate her life and do things that will make her happy and proud of you.
She is just watching over you all the time now, you just can't see her but she is with you every where you go and whatever you do. Talk to her when you're happy and when you're sad. She is just listening.
They are never really gone they just transition to become spirits, their bodies might be gone but in spirit she resides in your heart always.

Go on with your life, do the best that you can which you think she is proud. Always think and reminisce on the times when you are in your happiest with her.

We all have to succumb to our deep sleep it's just a matter of who will go first.
If you keep on moping about her being gone, do you think that's what your grandma wants you to do?