I have 3A hair and I found this board more helpful than naturally curly, personally. Actually the only board on naturally curly that I ever visit is 4a.
I take care of my hair like most of the type 4s on this board, just with less DCing and less moisturizer. Most of the time I don't even use a moisturizer at all. I DC maybe once a month.
But if your friends hair is damaged, she probably needs more of that.
My regimen is daily cowashing, sulfate free shampoo once a week, protein (aphogee or a protein heavy dominican conditioner) 1-2 times a week. I finger detangle every time I cowash
I try to avoid styling products because my hair is very fine and gets dull with build up very easily.
I can't wear braids or twists. That would be a good protective style for a type 4, but for me it's way more combing and product than is necessary. My hair just does not hold in styles like that and my hair is so fine that no matter how loose the braids are it's always too much tension and will give me breakage. I wonder if your friend has that issue with her weaves
As far as styling goes, I don't use heat or a comb. My hair does not tangle easily and a daily finger combing in the shower is enough. If I put leave in and oil on, I can wear my hair down and curly without any other product except maybe a frizz serum on a very humid day.
If I want waves, I put my hair in 2 pocahontas braids. If I want straight hair, I put day old hair in a bun.
The biggest mistakes I made in the past were just doing more than my hair required; combing and brushing, heavy products, and relaxer.
Since my hair is so fine there is really no saving it or hiding the damage once it gets all broken and full of split ends.