She is not ready for that kind of dexterity.
I taught all three of my children at home, using a renowned program (Cursive First and Spell to Write and Read.)
There was a reason that formal education didn't start until kindergrten. Just as we can't force a 10 month old to walk, we cant force a young child to be ready to write. There is a lot of dexterity that is involved including small motor movement, hand - eye coordination and the readiness of the nervous system. Age 6 is a good time for the 'average' child to be ready for that, hence, that was the set age to start school.
For the early years, pre k, I let the child hold a crayon the way they want. They are typically going to grasp it with a fist. that is ok. The big chunky crayons and fat markers are designed for this. The child may wish to write their name. You can try to help but for the most part i would let the child just explore. Dont try to make a child hold a crayon or marker int he pencil grip style. Only a pencil should be used for that training.
Formal penmanship education did not start for my son until he was 5.5. pencil grasp was a huge struggle, so I waited another 4 months for that part of it. (so at first we wrote letters in the shoebox-sand box with our finger). That 4 months made the difference in his readiness. My girls were a little earlier, I want to say ...maybe 5 or 5 and a half.
It is not just the way the child holds the pencil. It is also how the paper is tilted, the placement of the other hand on the top of the paper to hold it in place, the placement of both feet flat on the floor with the chair at the right height, and the chair pulled up to the table so the child's back is straight. A regular sized number 2 soft lead pencil should be used, not a fat pencil (made for fist writing) or markers. If you can't get the right finger placement on the pencil, they have little rubber pencil grips you can put on the implement. If the child is squeezing the pencil too hard, they might have too low of a grip - it should not be at the very bottom. Also that kind of squeeze will produce fatigue FAST so it must be corrected.
The very sad thing is they don't teach cursive in many schools anymore. What a huge shame, because you can write so much faster in cursive. I taught 2 of my kids cursive only. They learned manuscript on thier own a little later. By the time they were in the last part of second grade they had beautiful penmanship. I would have never believed it had i not seen it with my own eyes. I think the schools dont teach it anymore because they assume all the kids will be using computers to write. But truth be told, there are a lot of brain- eye- hand connections that need to be made in the brain at a young age with WRITING by hand, and if they are never formed, there will be learning gaps.
Fear not mama. Re-introduce it every 4 months until you see that she is ready, and when she is, you will know it. If she is not, just wait. Otherwise you are banging your head against a wall for nothing.