Another thing to consider, and which may help convince your daughter, is that snakes are rather lacking in manners about when & where it is ok to relieve themselves.

If you really want to read more on the subject, there is a long thread about it. I haven't read the entire thing, but what I did read was mostly more of what you've been told here: not a good idea.
http://www.ball-pythons.net/forums/s...ad.php?t=55752