She's not entirely irrelevant. She's in there partly to show the conspiracy, and partly for the same reason Monica is: providing a defamatory story about Vic that fans would treat as credible because she's a co-worker. If she wasn't part of the suit, the defense could point to her and say "if tweets are so damaging, why haven't you sued any other VAs for their story, like Marchi?"
Without her, there's still conspiracy and defamation shown by the other defendants. That means she's non-critical to the overall suit, instead of wholly irrelevant. She earned her place in the lawsuit, even if it was a long shot and Ty only included her as a strategic gesture.
(Considering she has the one good lawyer on the defense, maybe the tactical play here is to let her go without appealing her dismissal, getting Sam Johnson out of the picture. The more Lemoine has to be the face for the defense, the better.)