There are quite a few talent agencies where they can send their photos to, especially in Las Vegas, just have them do a Google search for "Trade show modelling" A few years ago I built quite a few glamour websites for women in BC and Alberta that did this and most of them had been in the business long enough that they didn't need to use an agency, but to get her foot in the door thats probably about the best way to start.
there a ton of model places in vegas ,they use girls for most conventions.you might try google or call the las vegas visitors burea of turism maybe they can lead you in the right direction
Here is one such company that does more than just Vegas trade shows also. http://www.models4tradeshows.com/
