Alright here are the quotes I have for Keiko. These quotes start pretty early because like Koenma doesn't appear in all of the books. So here's what I got for now:

"Smooth pick-up line, buster."-Vol. 2

"Good gosh!! Yusuke's practically buried!!"-Vol. 2

"They're going towards Yusuke's house!"-Vol. 2

"God, now it's making me all weird!"-Vol. 2

"Underworld? What's that?"-Vol. 6

"She said you're working for a private detective. Ho, I see. "Underworld" is the name of his agency!"-Vol. 6

"How can I calm down?! We almost died because of Yusuke!"-Vol. 6

"Yusuke, your friend's in danger!! And you're taking a nap?! You heartless creep!!"-Vol. 6