Should I get her to change textbook?

So I got my first tutoring client, a year 7 Japanese beginner who didn't managed to get into Japanese course in school but would like to study Japanese. Her mother asked me to go through and teach her from a textbook called Obento, this textbook is apparently the one prescribed by NSW schools for year 7 and 8. The thing is, this textbooks is so sh!t and random and immature (very cartoonish ) and I personally find it a waste of time for anyone to study it when there are much better textbook such as Genki and others.

If you were in my position, would you tell her mother that this textbook suck balls and change to a more worthwhile and tested textbooks (and RTK) within the Japanese language community and maximum her daughters growth or teach her daughter whatever her mother wants which is just the Obento textbook?

Because I fear that if I asked her mother to switch to a different textbook, she might not appreciate my effort and think that I am trying to divert from the school course, which is what she wants for her daughter. Her mother obviously doesn't know what textbook is good or not, but I just feel every lesson is a waste of time and I feel guilty taking the tuition money...

IMHO, private teaching is a "service" business. You give what your customer wants.

That said, I have seen good teachers build great lessons from crappy textbooks (with "supplements").
So, I think it is all up to you.