I actually love Dawn, and she's a very important character, that's not given enough credit. I really love seeing how she matures throughout the series. Like Buffy, she's strong willed, brave and has a sarcastic sense of humor. Dawn really steps up to the plate, helping with research, even learning demon languages to help the gang and is totally unafraid to get into the thick of fighting.
I don't think there was a specific "moment" that made me realize that Dawn was going to be more than just "Buffy's annoying little sister," or made me like her, rather I think it was a culmination of many things Dawn did, but if I'd
have to choose a moment, it's how maturely she takes learning that she could possibly be a Potential. She's obviously very disappointed she's not, but handles it very well.
Also fun facts: aside from Buffy and Willow, who appeared in every episode of
Buffy the Vampire Slayer, Dawn is the only character to appear in every episode after her debut, and has the final line, "
Yeah, Buffy. What are we gonna do now?"