color usually damages. I can't say if the damage will be immediately or down the line. From my experience, damage is inevitable with color unless you're using a temporary dye. Also, you won't be natural once you apply those chemicals to your hair.
Texture wise she will still be natural though and I think that's all she cares about.
I'm sure there are people who have colored with success OP. It's not color that damages your hair, it's technique and practice.
I wore blonde relaxed hair for years and never had any damage. I kept my hair conditioned, used minimal to no heat, and kept it moisturized.
I plan on coloring my natural hair too before this year is up. I have densely packed fine strands.