VC Andrews's situation is complicated, because her name is a brand that's outlived the original author. The writer Virginia Cleo Andrews only completed a handful of series herself before she died in 1986. The 'Dollanganger' saga, which starts with 'Flowers in the Attic', is her only major series she fully wrote. The 'Casteel' series was nearly done, but the final book, 'Web of Dreams', was finished by her ghostwriter from her outlines. Everything after that—the 'Cutler', 'Landry', 'Logan', and dozens of others—are entirely the work of Andrew Neiderman, writing under her name.
So, if you mean books with the VC Andrews byline, yes, there are many completed series. The 'Dawn' trilogy is done, the 'Ruby' series is done, they all have endings. But if you're asking about series the real VC Andrews personally completed, the list is tragically short. It's a key distinction for purists. I read the early ones and then tried a later 'series', and the voice just felt different, like a competent imitation that missed the specific, visceral grotesquerie of the originals.