While Harmony has lived in Drusilla's shadow since meeting Spike (( sometime between May 1999 and November of that same year )) they have only met once. In 'Crush', Drusilla comes back for Spike and meets an irate Harmony. Dru is amused by the pet names Harmony calls Spike and later encourages the blonde in taunting and hurting Spike.
Pretty much just Spike, whom she dated from Season 4's 'Harsh Light of Day' to Season 5's 'Crush' on and off again.
They're both utterly adorable and have each moved on from the bleached wonder.
Dru wouldn't hesitate in scooping Harm off her feet and hightailing it to France.
Assuming Dru could put up with Harmony's rather ditzy ways and young ideals and that Harm could put up with Drusilla's eccentrics and fondness of dressing in 1800 fashions, they could make one hell of a duo.
Dork-us aside, 'Crush' is the only real Dru/Harm episode. Boo-boo-bear doesn't quite make the five star ranks, but 'you tell him little girl' was quite cute.