That's pretty much Tallulah's constant look, lol.
Unless she's asleep, or just on the verge of falling asleep and trying to figure out how to get snuggled in even closer.
It's a fun contrast to Kharma, who is incredibly intense, but is cat-like, in that she hides it, and will seemingly be dozing or daydreaming, when, in reality, she's zeroed in like a laser and may just explode into action before you can begin to blink. She's very, errr, SUDDEN.
Tallulah you KNOW, you can see it, that she's quivering with anticipation for something to happen.