Long colourd curly hair

I havte a client with long past waistlength very curly hair with foils through the top she has her hair professionally straightned once a week.

It is getting dry on the top where she has the foils so we are going to cut them down to only doing a few thicker ones on the top so as we can just do the regrowth on them.

I perscribed her some davones shampoo for dry damaged hair as it is very conditioning I have found it a great product but I also sold her a protien treatment and a hair mask to follow which is a very deep conditioning one,

How often should I get her to use the protien treatment? I dont want to overdo it yet I feel with the straightening & chemical damage on top it is necesarry, what do I look out for in regards to when I tell her to stop using it for a while , I told her to do it once a week will this be too much?