Well, i didn't do the unit 1/2 of Psychology, English Language, Further OR Physical Education, and I have not been affected in the slightest. You don't even need 1/2 it barely helps you most of the time, however, i would have preferred to do it for English Langauge but the others it's definitely unneeded.
Don't worry about it, tell her to focus on aspects of 3/4 if she's willing to self-study unit 2, as that's a better use of time..