Why would viewers go to a site with only ten girls? Even assuming all ten girls were on at the same time all day everyday... It seems .... Boring.
It feels like they would have to specifically go there to see a specific girl or type of girl. So a girls current member base? If that were the case she could cut out the middle man and arrange Skype shows for alll the dollars. I know you said there was existing traffic... But.. like.... How can you know that traffic will be interested in the narrow selection of girls your site will be forced to have.
Internet is usually a numbers game, lets say you have x amount of traffic and a camsite with 100 girls, so maybe 10 % of the traffic finds a girl they like and spent money on, now assume a site with 10 girls, here maybe only 1 % of the traffic finds 1 of the 10 girls worth spending money on. If you have enough traffic it can even work with 10 girls. But in general I agree the more choice the better...