I think because her hair is so dry, it would just straighten to be very frizzy and still hard to maintain. Like, my hair only has a good, straight finish when its generally healthy. Plus, then she wouldn't be able to wet or dampen it to form the bun. Even if she did choose to straighten it, it would be better to get it healthy first so she didn't cause a lot of damage. I don't think product use and brushing is that harmful, i think the pulling of the bun and lack of deep conditioning is. Also, it sounds like her scalp is oily and she would have to shower every few days. Besides, her hair is 2b. I don't think it'll be that unruly when she conditions it more.
Fine Texture, Normal Porosity, Normal Elasticity. Dyed to brown a few months ago.
Lowpoo: Trader Joe's TTT Shampoo
Rinse Out: Yes to Carrots, AOHR, Aubrey Organics Rosemary Peppermint
LI: Yes to Carrots
Stylers: Shea Moisture Curl Enhancing Smoothie, LA Looks Sports, Suave Professionals Captivating Curls Whipped Mousse