I've never posted to you before, but this is an interesting thread...
So W is on a search for the meaning of life...buddhism one week and wicca the next. Doesn't that sound like the typical teenager to you, and isn't that what the MLCers are often compared to?
Have you thought about just taking her seriously and asking her what it is about these belief systems that appeal to her? She might feel validated and you might learn something, either about her needs, or the philosophies, or both.
I don't know much about wicca, but I do know that we catholics with our transubstantiation doctrine have turned a few stomaches too over the years. Wicca may not be nearly as bad as you think, heck, at least she is searching for something to provide meaning.
Good luck, you have in interesting situation although I'm sure it is much more interesting than you ever wanted!