I don't know how much of that is true. I mean it obviously is from Buffy's pov but Buffy has a martyr complex imo, she just likes to blame helself for everything that goes wrong, so I wouldn't hold her opinion as the truth. But even if it is, it would just mean that Joyce and Hank were in disagreement over Buffy's situation and how to handle it (and maybe the internment issue we are discussing in the other thread could just as well be one of those disagreement), so given that Hank is the one to leave his daughter it's easy to assume that Joyce was the supportive parent.