I think any loss of a family member (no matter how old, or how well-lived a life they had, or how long they've been ill) is a very big deal to our emotional brains. It's how we're wired.
Your grandmother does sound like she had an amazing and very full life. I'll bet she had wonderful stories to tell, too.
Grief is a funny thing. I lost my mom when I was 24. I went through every stage of shock and dismay and grief that there is possible to have. And periodically, I still find myself crying and missing her. I'm clearly not done mourning her. And it's been well over 30 years since she left this plane.
Give yourself a little time and space to honor her memory. Trust me, you'll be glad you did. Perhaps write her story down for others to enjoy and take inspiration from.
With sincere condolences, MG