My first thought was that this must be a typo for "describir", and I posted an answer to that effect, but Billh, who agreed, reminded me that "prescribir" is also used in marketing, and this made me reconsider. My general rule is that you shouldn't assume a typo if the text makes sense as it is, and I think it does. What would be a good idea, to be on the safe side, would be to add a note to the effect that "prescribir" seems to mean this, but it could be a typo for "describir".

"Prescribir", along with "prescriptor" and "prescripción", are quite common terms these days for what could be called consumer motivation. The idea is that a "prescriptor" is someone with a certain authority who influences consumers to make them inclined to buy a given product. This seems to me to fit the context very well: the bloggers effectively promote the fashion show, reviewing and recommending items in it, so that their readers end up buying them.

I have encountered "prescripción" in retailing in my own translation work, and it's well established. There have been several previous questions, which offer a range of solutions in English. Here are some:

http://www.proz.com/kudoz/spanish_to_english/marketing_marke...
http://www.proz.com/kudoz/spanish_to_english/marketing_marke...
http://www.proz.com/kudoz/spanish_to_english/tourism_travel/...

The word "prescriptor" is actually found for this in English:

"Are bloggers prescriptors? An ongoing debate today at #sial #Paris #WineInnovationForum"
https://plus.google.com/101281207011417565395/posts/A67rwayP...

"True there need to be some critical attention to “ambassadors” i.e influencers that also are buyers and prescriptors, but I don’t see brands ready to move beyond this initial first step."
http://socialmediainfluence.com/2012/06/05/buddy-media-vitru...

However, I think the best word here is probably "influencers", which is widely used in this sense:

"The Foodbuzz Community is made up of the Foodbuzz.com Hub and over 1,500 Featured Publisher Food Bloggers, who are Food Experts that act as influencers to the larger user base. "
http://www.mediabistro.com/abm/joblistings/jobprint.asp?joid...

"Mapping mommy bloggers: Using online social network analysis to study publics
Katie Stansberry
University of Oregon, USA
[...] As one of the first publics recognised by marketers and communication professionals for their power as influencers, mommy bloggers are one of the more established online interest-based network (Lopez, 2009)."
http://www.prismjournal.org/fileadmin/8_2/Stansberry.pdf

And so on. Lots of references to bloggers as influencers.