What can you suggest to cheer me up?

I know what it is liked to lose a loved one my sister passed away not too long ago. I regret what I said about her to my mom the day before she passed and I will always live with that.
Hang in there and give it time and you and your family will be in my thoughts and prayers.
Remember that crying helps crying has helped me through the last 2 depressing moments in my life.

This is going to sound weird and a bit cliched, but simply talking about it can do wonders, often because if you tell someone, you'll then have a confidant as your situation progresses.

Awww, this'll pass. I've lost both grandmas from either side of my family, as well as a cousin. Hugs upon hugs to ya!