Welcome to the bb forum and thank you for sharing your story. I am very sorry for your loss.
It is so nice that you and pop were with nan when she passed. She didn't go on alone, she took all that love with her.
Unfortunately the price we all pay for great love is deep grief when we lose someone. Everybody grieves differently and there is no right or wrong but here are a few ideas for you to consider.
Talk to your nan. It's perfectly okay to talk to the dead and a lot of people do this to cope with grief. I lost my mum in Feb this year and I've put a large photo of her in my lounge room and I talk to her often.
I also talk about her with my husband and children. We share happy memories and laughter and it helps to lessen the pain. Perhaps it would help to visit pop and talk and lean on each other.
You might also want to start a journal, where you can write down happy memories and all the things you want to remember about nan. Add some photos if you like and you can spend time with nan by working on your journal.
I know it's really hard right now. Give yourself time. Be kind to yourself. Take it one day at a time.
Kind thoughts to you