First of all, she did masturbate in the tub, using shower head. Arching her back (and showing her breasts) was when she had orgasm.
Second, many girls with long(er) hair prefer to wash hair standing over the tub. Reason for this is because there is a lot of hair to was, which is *not* easy and this way is easier then standing up. It does not mess with your eyes / face and you can let the weight of the hair hang down. So that has nothing to do with her (not wanting to) showing breasts.
Is this forum slowly degrading or is it just me?