Can someone help me with reading order of Harper Row story?

Hey guys,
New to this site, and reading comics / graphic novels in general. I have a decent understanding of Batman as far as DCAU, movies, and the Arkham games but to be honest, I've never been much of a comic reader as the sheer number of issues and the different series and sub-series within each superhero has been overwhelming.

Lately, I've really gotten into reading the collections I buy off Amazon. I just finished reading Batman: Volume 2 The City of Owls (The New 52). I was really digging the introduction of Harper and Cullen. I don't know why, maybe it has something to do with sidekick origin stories and the idea of an average person being inspired by and getting closer to a reluctant Batman. Do you guys know where I can continue her story? I was actually disappointed that the next comic in that collection was about Mr. Freeze. Don't get me wrong, that was an awesome story but I just wanted to see how her relationship with Batman would continue. I'm currently reading Volume 3 Death of the Family so it's not in there so far. Is it in a different sub-series like Detective Comics or Batman Eternal? Please let me know the collection and not the individual issue number because I have a hard time following those. Thanks and glad to be on this site!

you should read batman eternal indeed, she appears in several issues, and it's a great story. she does appear, I think ti's in Tec 21, but she doesn't do much.

She's not a character with a continuous story. She just appears every now and then, in one-offs and as a small part in a larger machine. Batman Eternal is probably where she features most prominently though.