Ah, I was going to come back to answer this and see it's already been done! I vaguely remembered KLS being on Jump Street, so I checked out her IMDb page and saw that her episode was called Change of Heart. Since I have the DVDs, I checked out the ep last night. I didn't know it was on YouTube
Anyway, the episode was from Season 4 (aired in Jan. of 1990, I think IMDb said), and Johnny was on his way off of the show by that time. He'd actually been trying to break his contract for a couple of years and they finally let him go, and by season 4 he was only in about half the episodes. In some of them, like this one, he would only appear briefly in the "precinct." IMDb didn't even list Johnny as being in this episode at all, and when I mentioned the episode title to other Depp fans yesterday, nobody recalled it very clearly offhand. We wondered how KLS and Johnny would ever have interacted if he wasn't in the ep (or only in one scene). But some guessed that perhaps she visited the set in preparation for doing her ep, or perhaps the show shot scenes from more than one ep simultaneously. Or maybe they even did some promos together for the show. Who knows?
Either way, I think it's so cool that they got to cross paths all these years later, and it was so gracious of her to send him her books!
Cathy