I think Grace would find the Perfects...interesting, given their bloodline and abilities.
They'd psychoanalyze the hell out of Todd. While they probably wouldn't be able to read him well, if they watched him long enough they'd know he's hiding something. And they'd probably be impressed by how well he's doing it.
Felix on the other hand lol, Grace would be able to read almost flawlessly. They wouldn't magically know all his secrets, but if they were around him at the right time, they'd notice his little changes in behavior when he's angry, sad, whatever. Which truth be told anyone would notice if they know him well enough, but Grace would be able to pinpoint it right away.
Grace is a teenager just like the other surface characters (and this is one thing they don't lie about) but they're seemingly wise beyond their years which can be especially frustrating to those who are only a couple years younger than them at most.