No, I would never omit any notes from a piece, at all costs. If she can't reach an octave securely, then I don't know what to tell you (her). An octave is really a requirement for classical literature- I would suggest at least avoiding Chopin anyway.
Chopiabin: Yes, I do almost all of the repeated arpeggiation that way, pretty much because I originally learned it that way and it is engrained. It works quite well for me, but it definitely would be better to do it the 'correct' way- I'm just too lazy to go back and work on it.
Dj: Sorry, that was a typo. I meant 521133- but this is only for the first part (the part all on black keys). Once you get into the C G# C arpeggiation, use normal fingering (532123) and just turn the wrist. If this is too awkward after practice, probably convert to 521212.
Hope this helps.