okay layla, looks like she's having difficulties....so in a nutshell...this is what she told me
It is perfectly okay to go long periods of time not "washing" her hair, you may need to use conditioner in between, but traditionally washing is not necessary.
She also mentioned a round soft bristled brush that might be easier on her...or a WIDE toothed comb. Brushing while IN the bath is best, combing conditioner in. An adult conditioner is okay, although they DO sell baby/toddler conditioner. Just be careful of the eyes.
Now this is ME talking, I would plat/braid her hair after a bath, and leave that in for a couple days. And it might give you more longevity for keeping the knots out of her hair
Sorry it took so long to get back to you...hope you didn't cut it!