No I’m sorry there’s no feature in the theme to accomplish exactly what you’re asking. The way prettyPhoto works with grouping images together into a lightbox is by taking all elements on the current page linked to prettyPhoto with a certain gallery ID and then grouping them together.
So, for example, all of these would be grouped together because they all have the
So, you’d have to come up with some creative way to use prettyPhoto yourself like maybe having a group of images that are hidden or something like that. You could possibly have all your images there, but only show the first one of each gallery, and then maybe wrap the others so their hidden to the website visitor.