My clients before pic is the result of her brushing trying to flatten it, I should have took pics with some pinned up too in hindsight as it was really curly and frizzy underneath, the hardest part of finishing was her natural kiss curls at the front but we got there. I think this would be perfect on your client and kind too, have a look at the site and do some googling.
I would look into both options discussed to give your client the best information possible to allow you both to make an informed choice, I will say there is no sensation with rio keratin but you do need to be ventilated LOL
Keep us all posted on your findings and best of luck
K x
BTW, my client did loads of homework herself once I discussed it with her due to bad experiences with relaxers previously, she said her hair had been left dull and lifeless and was so excited and now the results speak for themselves x