Why would you go from 5x5 to 2x20 or 3x15 with probably minimal weight?
Why not go to something like 3x8? This way she could still do a decent amount of weight but she'd be able to change up the rhythm and maybe not get so bored.
I guess my reasonong would be that 1) It provides more variation from 5x5; 2) Since she would be lifting heavy with 5x5 either once or twice a week, it would help with recovery; 3) It would exhaust her more and make her feel like it is helping with her goals; 4)She told me she hates doing 3x10 because it is boring; 5) Girls want to use high reps no matter what you tell them.
I am not saying that those are the best rep schemes, but that is why I was considering them in addition to 5x5(increasing weight each set). I was also thinking that she might like doing a circut on the straight set day to save time and boost aerobic benifits.
I'm not even sure 5x5 is the best idea but I think she would like lifting heavier weights for motivation.
Here is a better illustration of my question?
Mon - Workout A - 5x5
Wed - Workout B - 5x5
Fri - Workout A - ?x?
Mon - Workout B - ?x?
Wed - Workout A - 5x5
Fri - Workout B - 5x5
Mon - Workout A - ?x?
Wed - Workout B - ?x?
Fri - Workout A - 5x5
Mon - Workout B - 5x5
Wed - Workout A - ?x?
Fri - Workout B - ?x?
Looking at that, maybe 3 seperate rep schemes would be simpler. Like, M-5x5,W-2x20,F-3x8. I Dunno, looks boring.