Batman (1940) Issues #139, #141, #144, #153, #159- Bat-Girl’s origin story and later appearances
Secret Origins Annual #3- a look at Titans West, Bette’s reasoning for becoming a hero & her relationships with other Titans
Hawk & Dove Annual #1- shows Bette’s personality really, really well. She’s flirtatious, badass and actually pretty funny
JLA/Titans-it gives a good glimpse at Bette’s fighting capabilities as well as more on her crush on Robin
Beast Boy (2000)- a huge, huge point for the character. This is basically her turning point and it’s where you see the first appearance of her best costume
Titans Vol.1 Issues #35-#36- a good insight to her character, during a more lighthearted adventure
Titans Annual #1- where Bette Kane does not take shit from anyone and is an official badass™
Young Justice #21- Bette and Cassandra Cain in the same comic
Batwoman Elegy- the start of N52 Bette and a pretty good showcase of her character
Batwoman (2011)- a bit iffy on this one, but it does have her transformation from Flamebird to Hawkfire
Other comics:
DC Bombshells Issues #1, #19-#21, #37-39 & #55-57
Young Justice (2011) Issues #20, #22, #23 & #25