......So because of the whole 3-in-1 deal, I just had the random idea of what if the Moirai, the three Fate sisters from Greek mythology. Mostly since I'm not sure if Brahma-Vishnu-Shiva can be considered as "one" essence given how although they're in a group, they're more like individual entities whereas the Moirai are always a trio and the theme is similar to what you're going for (fate of life and all that).

Since they're spinners, could use spools of threads and have powerful scissors as a weapon, capable of cutting through a lot of different materials. Of course she wouldn't be able to cut anyone's life, but perhaps being able to read if their life is in danger.

I CAN GIVE MORE IDEAS but I'll wait to see what you think first lmao