a little more info from my Irish dancing days:
Slipjigs are exclusively danced by females (although occasionally a male might learn it if he's a total keener or the only male in the class, only females would compete or perform the slipjig).
They are also exclusively danced in soft leather slippers (unlike jigs and reels which have both soft-shoe and hard-shoe versions). The slipjig steps do look quite light and feminine, more like ballet than rhythmic stepdancing. You sometimes see the girls leaping as if they were jumping hurdles, and seeming to remain in the air - that's a slipjig step.
And I think - though I'm not absolutely certain - that slipjigs are distinctively Irish. They don't seem to exist here in heavily-Scottish-influenced Cape Breton.