Lawyers on behalf of Paige (officially "alone," as plaintiff) filed a lawsuit (in October 2014), claiming that Paige was assaulted when Abby threw a chair, as you probably remember from Season 2. Here's a video link.
The only cause of action in this lawsuit can be summarized by some of its text: "16. Defendant MILLER intentionally engaged in conduct that caused Plaintiff PAIGE HYLAND to reasonably believe that she was about to be touched or harmed in an offensive manner, namely by hit by [sic] a chair thrown by MILLER."
At the time it was filed, the judge had already indicated she was likely to throw out most of the Hyland's other previous joint lawsuit (filed on behalf of Kelly, Paige and Brooke combined in February 2014), including all the parts claiming abuse against Paige (and the judge did just that shortly thereafter.)
IMO, the lawsuit filed on behalf of Paige (alone) was entered at the urging of Kelly (and by the same lawyers representing Kelly in their joint lawsuit), and the motive was as a nuisance lawsuit, further meant to damage Abby's public reputation via tabloid reporting.
I think I should add here that Abby was being stupid, rude and insensitive in the scene where she throws (one could say drops) the chair, for a combination of reasons (and not just what she did with the chair - which anyone can see from the video was not thrown/dropped in Paige's direction.) She said things about Kelly, and dismissed Paige from class in a way that was pretty heartless. And that's when Paige got really upset.
And Abby did upset Paige. But upsetting someone is not assault, and it seems far-fetched to me to think a judge would decide that's what happened when that scene was filmed. It'd be like lawyers arguing that Kelly assaulted Maddie when she did something very stupid and foolish in the Bronx; most people in the room were upset/scared/shocked by what she did, but only one of them was even arguably assaulted by Kelly.