Guys it`s just a system..same as we all get/wear... there`s no particular reason why you shouldn`t give it a wash if you like...she`s probably just trying to `save you the bother`.. I always give mine at least one [light] wash before a cut-in. Simply mix 2 or 3 teaspoons of shampoo into a sink of lukewarm water and sit the system in it, base side up... leave it for 3 or 4 mins..then gently dunk it in and out a few times..then empty the sink and rinse under running [lukewarm water] through the base ...gently squeeze off the excess water and then sit it on a towel and blot it dry..don`t rub/knead the hair either in the sink or in the towel. Sit it on a head-form and wait until it`s nearly dry before gently brushing it while it`s sitting on the head-form,or some round item --you can even sit it onto your head -- as this will keep the lace `flat`[non creased -up anywhere] Use a brush with rounded tips ..the black one in the top pics here is what I use http://www.denmanbrush.com/acatalog/Freeflow_Vent.html
No need to condition the hair --it`s brand new and in top condition....you`ll see loose /stray hairs in the water in the sink too--that `s normal...also, quite a few hairs can be coming through the underside of the base when it`s dry -- I always just snip them off with a scissors but leave your stylist do it if you prefer....systems can take up to a fortnight to `settle`in ..the wave can be `strong`and the hair `lively`...giving it a wash before a cut-in can help to relax it a bit..actually makes for a more accurate cut-in in my opinion.... most stylists will leave a little `extra`length on it and you`ll go back in a week or so for any `tweaking` as the hair settles-in.

Yeah I'd DEFINITELY wash, I do it 3-4 times before cutting in, plus mist with a 'water/conditioner' mix inbetween times lol. New hair tends to a bit wiggy looking (depending on the density) & as Paul explained, washing hairpieces calms the hair down. If you actually wash it first for your piece of mind (as most wearers do), realistically, how will the stylist ever know? Regards

Yeah that's more or less what I thought. However, I am still of the opinion that you should let your stylist show you proper maintenance first, which includes shampooing, if this is available to you. But it's not like you're dying the piece or anything, so as Paul said, you can't do much harm giving it a wash.