I held it together. Why?

TLDR
My grandma (75F) died unexpectedly from a major heart attack during a visit from the UK to India. She had dementia, and while I’m sad, I feel... strangely detached. I barely cried, stayed calm, and focused on helping my parents and guests. Now it’s super late at night, and I’m avoiding being alone with my thoughts. I feel guilty for not feeling “more” grief. I feel awful that I don't feel awful, and I'm wondering if 1. anyone else grieves like this and can relate and 2. if anyone else has been with a person who grieves like this, and if it's jarring to see them just chug on business as usual.

My paternal grandma (75F) and grandpa (75M) came to the UK from India for a visit, and my grandma died today very unexpectedly of a major heart attack. She had dementia, and I honestly almost felt... glad? I knew that after this trip, the next time I saw her she wouldn't know who I am.

But, I (17F) knew it from the moment the paramedics mentioned the specific artery they thought was blocked (I am a very health anxious person), that she wasn't coming back home. I knew it in my soul, so when my parents (48M and 48F) called us there today, I completely underreacted.

I feel awful, and I am grieving, but I completely held it together today. I barely cried. I very calmly asked the nurses if I could leave the room with her body, asked them to cut my nails so I wouldn't scratch myself anywhere, and got them to explain all the medicine for my peace of mind.

We came home, and our LOVELY friends helped my parents through every step. Drove us, talked to cremation services, made us food, were angels. And I held it together. My dad was on the sofa, I was washing their waterbottles so when they went to sleep they could have their favourite ones. I cleared the fridge, I talked to guests about their kids and their lives. I barely told my friends, and then acted like nothing happened. It's 2am now and I'm on a call with different friends because I don't want to be alone with my thoughts about this.

I feel awful that I don't feel awful. Seeing your parents cry, feel so much guilt over this is an experience that you simply can't ever forget. It's all raw right now, and I'm sad, I feel it physically, but I feel so detached from that. Is it normal? Any of you had experiences with that? Specifically, have you been with someone else who grieves like that, and is it okay to deal with? Or jarring?