Erica, did you know this about your grandma prior to her being sick... or did she share that with you in that moment? Sounds like she was able to reach you somehow, and give you the strength you were needing.
I related a bit to this because I was closer to my gma, more than my mom. As far as I'm concerned, my gma was more of a mom. When she died, I had a really tough time letting her go. It took a couple of years for me to really come to terms with it.