Another thought on the Buffy/Dawn relationship and why Buffy is so harsh sometimes it that Dawn is possibly who Buffy would have been without the slayer calling... If Dawn is "made" from Buffy, but without being a slayer she is essentially living Buffy's life without the burden of responsibility that being The Slayer is (a major theme for the show). There are a lot of quirks and temperament things that are pretty similar between the sisters - a pragmatic intelligence, a macabre sense of humour and when Buffy is without her powers she is a lot more clumsy and awkward like Dawn is initially too. It just a thought, but one that has stuck with me and adds another layer of friction for the sisters on top of an already very relatable older/younger friction (as an older sibling I very much agree with what you are saying too)
