Credit where it's due to Ms. Simone. We all know her first run on BoP is the best (Sorry Dixon fans, you're the minority on this one
), but she did an incredible job of drilling the idea of the trinity of Babs, Dinah, and Helena into people's minds. The book was just Babs and Dinah for a MUCH longer time than when it was the three of them, as setting aside where she was part of the team briefly,before the ongoing started, in Simone's run, Helena was only around for 20 issues before Zinda showed up, and pretty much got equal ground with the others.
Charlie is a favorite of mine, Babs as Oracle aside, she's my favorite of any of these characters, and at the very least, she showed up and was created specifically for the team, before the mass recruitment happened. Even so, I can still see people saying she isn't "necessary." Zinda though? Even if Helena wasn't active on the team for some of it, it was still the 4 of them in the book for as long as it had just been the three, so in my mind, Zinda's as much of a core member as Helena.