Q.Is My Stapelia Vellitiae Ok?
I bought this stapelia vellitiae about a year ago and may have neglected it. Took a photo and showed a nursery and it had millie bugs. I was given a spray to get rid of them and seemed to work. Has a couple white stains on it still. I cut the tops of as they appeared rotten. I’ve re potted in premium potting mix advised by the nursery as it works similar to succulent mix. I have a new healthy looking shoot growing right under the bigger shoot.

Certified GKH Gardening Expert
It looks to be suffering from the infestation. I would apply a fungicide to mitigate any infection brought about by the insects. Recovery can take awhile, but with proper care will happen.
You can treat this like its close relative, the starfish cactus.
Here are some articles that will help:
https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm