Weeeeelllllll....Irrim wasn't not reading her mind. You know. Just surface thoughts! Had to stay on top of things and Liliana had forbidden her from reading Ignis' mind and neither she nor Jace had ever been able to read Liliana's, so clearly, this was just self-defense.

...Or something?

"Oh! I'm Irrim," she said. "Irrim Vesseren. Pleasure to meet you."

Because there had been no way Liliana was going to let Jace be the only one giving his surname to the child.