Complete all 40 of the Catwoman Riddler grid items
Yes, Catwoman has Riddler trophies too. They are much easier than Batman's to collect though and they do show up on the map as ? after Batman interrogates an informant. For some of them, Batman will have to open the area up for her, but the majority are easy to get to. Batman can't pick up the pink Riddler trophies. You have to play as Catwoman to get them.
They were all pretty easy to find and didn't take too long to find. You can follow this video for a walkthrough (thank you to LVIToHeathrowGaming on Youtube for the video).