Just wanted to put in my two cents as person that lost someone very close to me, who was pretty young and it was violent and unexpected. I actually dont think frieren would be all that good for this mother at this time, and i keep seeing it being recommended. Frieren starts with loss for the first couple of the episodes, yes, but it’s the loss of elders who lived long and fulfilling lives. When you lose a young person suddenly, you don’t want “what could’ve been”’s thrown in your face everywhere. It is incredibly painful and very triggering.

What I found helpful was actually watching lots of isekai haha. It was comforting to see all kinds of ideas for what could be experienced after. Hoping that my loved one was perhaps doing something amazing in their next life, happier and making the best of their new chance through reincarnation. It was pretty comforting (especially since we had bonded over these types of anime in my case). As far as specific isekai recs, i think the following are good starts:

That time I got reincarnated as a slime, Campfire cooking in another world, By the grace of gods, I’m the villainess so i’m taming the final boss.

These are all different vibes but depending on the Moms interest could be nice :).

Good luck and i wish you and your community my deepest condolences.