Any advice for dealing with grief from a traumatic incident

Trigger Warnings: parent death, pet death, drowning

Recently my mom passed away in a river accident.
She had brought her service dog (a German Shepherd) with her on a rafting trip with friends. From witness testimony, her raft got caught in some trees and as she was trying to detangle herself, her dog got spooked, and jumped into the river. My mom was tied to the dog, and they ended up drowning. They found both their bodies hours later.

I’m still reeling, and I’m in shock. It’s almost early morning and I still can’t get to sleep. I live in a different country and I need to head back to deal with her affairs. She was a single mother, so it’s up to me to figure things out. I have a lot of support, but it still feels so overwhelming.

I specifically would like any advice on how to deal with the “accident” part of her death. It would be one thing if she had died peacefully in her home. But the reason I can’t sleep is because my brain won’t stop trying to imagine what it must have been like in her final moments. The fear, the struggle, her body washing ashore and just sitting somewhere for hours until they could find her. How she must look like now. I will request they cremate her, the police pretty much recommended I don’t do a final look because of how she died. But the morbid curiosity is just there. I don’t know how to shut it off. I know she wouldn’t have wanted me to ruminate over it, but it’s almost like I’m getting the PTSD on her behalf.

I’m also so angry. Angry at her for thinking it would be safe to bring her dog on a raft. Angry at her for tying herself to said dog. But I realize this is more like “denial/bargaining”. My brain keeps making these angry scenarios where I’m yelling at her not to be so stupid. What would possess her to do something like this? But of course that’s just another part of grief.

I’m rambling, it’s late. (Or rather early?) I’m just really sad and tired. Any words would be appreciated.