>>211397612Age in comics is always a bit wack, but in the Bruce Timm continuity she's maybe 10 years older than Dick at the most.
Lets look a what we know: Harleen meets joker on the first day of her psychiatry internship and becomes Harley Quinn maybe 6 months later.
How old was she when she became Harley Quinn then? Let's say she started her bachelors at 18, she would have been enrolled in medical school at 21 and be 25 by the time of her arkham internship.
I think we're told explicitely that Dick is 18 by the time she becomes Harley Quinn, or at least that he's just started college at that point.
So she's probably 7 years older than him. It's a reasonable guess at least. And bear in mind the rape (lmao, can't rape the willing) happens many years later when Dick's way into his 20's.