Immediately after the party she murders Shenna's parents as her next job. I just read last chapter and I can barely remember what Shenna's convo with Serena was about. Now she's an orphan at a nunnery. Would that be the last we see of her? I don't suppose she'll become a vengeful antagonist or anything?
Her mother and her stepsister remain idiots, nothing changed there even after all those years. Their house is headed to ruin via social faux pas at this rate. But I'm not even sure that's really a negative for Serena who's already living her old life, just this time she has more money than she used to.