Best Batgirl yes...but character who wore the cowl, I respectfully disagree.
Cassandra Cain was the kid in 7th grade who got straight As, took home every trophy, and had this heir of invincibility. She even had a handicap so you can't even touch her plight.
I can't relate to that.
I relate best to Stephanie Brown. Bryan H. Miller broke fresh ground with brass cajones in his Bat girl. No you don't have to be the "The Darkness in my soul" type that is such a tired trope in the Bat universe. The best part about Stephanie was not her resilience against villains but against the Bat family. They rejected her. She wasn't good enough...which is funny because neither were Dick, Tim, etc when they started in this business. Yet, Steph has faced her own death. Has a dad who is a criminal. But you can't tell the way she fumbles along through being a super hero.
To bottom line it, she's a simple girl trying to get respect...with a healthy sense of humor.