My immediate instinct is to say "No, they definitely wouldn't", but then....I don't know. I mean, if you didn't intend to weigh in yourself, and didn't take any of the WW materials, and went solely to offer moral support to your friend, I don't see what the issue would be.
It's not like you would be costing them money or anything. I mean, what would they do -- kick you out? (Can you imagine?)
I say, find a location near you (well, preferably the one your friend will be going to! *L*) and just ask them. The worst they can say is "no", right?