May or Dawn because the last time I checked they both participate in Contests, which is Lisia's home turf (I am assuming we're talking about Contest Star with an Altaria from ORAS)

Could be Serena if she’s still in Hoenn learning about contests. May or Dawn might meet both Lisia and Serena.

WOW!

Maybe in a new arc involving Lisia and Contests, May, Dawn Serena, and Chloe might meet each other for the event.