
It will be ok to bathe her for the party using a mild shampoo :) or you could just wipe her over with a baby wipe! The advocate would have already penetrated the skin and be in the bloodstream and you can probably already smell it on her breath!
Advocate is rather strong though, so I wouldn't have jabs and worming done at the same time in future (or anything else really, anti b's, painkillers etc when worming with advocate) - in fact my puppy girl has had a GA and 2 sedations in the last month, so I left her worming until a week after the last sedation, which made her 4 weeks late! I have to use advocate every month :(
http://www.advocate-spot-on.com/4416.0.html