Hey There!
I wash once a week and I flat iron too.
I think she would be okay. I don't do protective styling because for some reason the formation of a ponytail breakes my hair off no matter how loose the ponytail is. I used to wear my hair in a protective ponytail and my ends were SHOT!
But there are some things that she must know. I would incorporate a light protein treatment in every 2 weeks, use heat protectant sprays (they won't protect the hair
entirely but they do provide some protection), good poo/deep conditioners, and a silicone serum (silicone helps protect the hair from heat).
I would also tell her to invest in a good SOLID (not coated) ceramic or tourmaline iron, a great moisturizer for those days that she needs moisture, and also a silk/stain scarf and pillowcase. All of the above things have helped my hair journey. Contrary to popular belief some people can maintain healthy hair with the use of heat, and thats from my own personal experience.