Yes plasonic is spot on. Not all of the newer girls do a full set of six, sometimes due to Deskbabes (Abigaile Johnson) and sometimes because they only do 4 or 5 in total (Saraliz).

Sandra Sanchez has one missing card a0128 "Action Girl", which was never released due to copyright reasons I seem to remember (there's a similar issue with one of Maggie's cards as well). The promotional photo set for "Action Girl" is available though.
http://gallery.virtuagirlhd.com/index01.php?dir=a0128

There are other missing cards from Carla Pacini and a few other girls that have never been released. Some due to corrupt footage or other technical reasons (e.g. Denisa K's Rubber Nun card), and I suspect some because the Totem team didn't like the outfits or just didn't think they would be popular enough cards at the time (I think these probably include Carla Pacini's remaining 4 cards).

I would love to see the remaining older cards that can be released, being released at some point. Maybe just for collectors since the quality wouldn't be up to current standards though. Maybe they should be released among the VG Classics, but for 1 ticket each or something like that.