i will never be over what the jenny-giles-buffy dynamic could/should/would've been and specifically how well jenny would've fit into it
giles can relate to buffy's struggles over an unwanted destiny and being crushed by the weight of her responsibilities but ultimately he was raised for a position of power while buffy and jenny were both raised to be expendable. buffy and jenny are both pawns in a war waged by someone else while giles, although deeply traumatized by his experiences, was always supposed to be on the other side of that.
on the other hand buffy's destiny, while cruel and tragic, was truly beyond anyone's control. ancient magical forces decided she's the slayer and there was nothing much to be done about it. meanwhile giles and jenny's destinies weren't actually magical or predetermined in any way. they were both hand-selected for them by their families — an act of cruelty by people who were supposed to keep them safe.
basically this is a long-winded way of saying buffy and giles's dynamic was left incomplete by jenny's absence
