My son is/was like this too. I try to have crayons and markers out for him to try on his own. We've tried all kinds of crayons, pencils, markers, etc. We have an easel, dry erase boards, etc. He's just not into it. We got him an etch-a-sketch for Christmas. He loves to write on it. He went from being able to write an "O" to being able to write many letters in just a couple weeks. He is really eager to learn how to write his letters now and is finally drawing, too. He is 4 years old. He has always held a pencil in a developmentally appropriate way. He just had no interest. IMO, I don't see a need to push writing or coloring on a child. I think especially at 2.5, the focus should be on developing fine motor skills so that they have the proper skills needed to hold a pencil correctly. If I were you, I would focus more on activities that develop her muscles in her hand than writing activities.
ETA: I dont know if you are on Pinterest, but if you are looking for activities to help your LO in that area, you can search "fine motor skills" and a lot will come up. I have a board just dedicated to fine motor skills
