While Batgirl fought alongside Batman and Robin — and had an on-again, off-again romantic relationship with the Boy Wonder — Batwoman has always been more of a loner.
She is Batman's cousin, but the two superheroes rarely work together. They tend to pair up for short crossover arcs in the comics, but Batwoman has her own comic and her own storylines going on most of the time. Batgirl, on the other hand, was largely a supporting character to Batman, at least until the 21st century dawned. Since then, the character has had a couple of different eponymous comics where she is the lead character.