Even then I think that in SG, written agreements between two people is not recognised before the law (maybe the lawyers/lawyers in-the-making here can clarify this). I suggest you find a way of registering the agreement so that it will be recognised in case she decides to sue you.
But seriously, if she wanna put the stuff on a banned website (that's so cheesy), either you got a very good lawyer in case the sh*t hits the fan, or you focus on taking pics of clothed people lah. Even chaperoning in this case is problematic (for a few reasons).
And you developing the pics for her on the day and giving her all the negatives and stuff has a few problems:
1) the person at the shop might identify you in the future
2) what if she can press that you hid some of the negatives (this is more of a hassle than anything else since even though they might search and not find, they will waste your time while searching and interogating)
So, bottomline, forget it man. Ask her to get a P&S and tripod and do it herself!
But then again, maybe you got a good lawyer...