Her dad's patronus is a lynx, and he's very important to her, no matter what she tries to say.
Cats and Iris work together: both are secretive, act confident even when they're making complete fools of themselves, indecisive ("open the door!" "...lol jk I'm going to stay inside"), and magical. This was a lot better before IJ ate it.
Pallas's cats are particularly emblematic of this, being apex predators but looking... well. Like this.
Their happy memory: Iris kind of went through a LOT of memories: her first blazingly happy memory of seeing her dad for the first time after the War, getting her wand at Ollivander's, her friends here at Gooseberry and back at Hogwarts. She ultimately settled on the first time she arrived at Gooseberry and nobody knew her name. Their attempt: Despite not being in DADA, Iris is pretty good at Charms and isn't too bad at advanced skills. She's seen basically everyone in her life not only cast this spell since she was wee but use it to communicate with from that time, too. That said, she's still a little miffed about the bonding activity and is still a little shaken over the Amortentia, so she's not at peak form. Are they in DADA or Occlumency?: Neither!