
Question: How did you decide that Molly Weasley would be the one to finish off Bellatrix?
JKR: I always knew Molly was going to finish her off. I think there was some speculation that Neville would do it, because Neville obviously has a particular reason to hate Bellatrix. So, there were lots of options for Bellatrix, but I never deviated. I wanted it to be Molly, and I wanted it to be Molly for two reasons.
The first reason was I always saw Molly as a very good witch but someone whose light is necessarily hidden under a bushel, because she is in the kitchen a lot and she has had to raise, among others, Fred and George which is like, enough... I wanted Molly to have her moment and to show that because a woman had dedicated herself to her family does not mean that she doesn't have a lot of other talents.
Second reason: It was the meeting of two kinds of - if you call what Bellatrix feels for Voldemort - love, I guess we'll call it love, she has a kind of obsession with him, it's a very sick obsession ... and I wanted to match that kind of obsession with maternal love... the power that you give someone by loving them. So, Molly was really an amazing exemplar of maternal love. ... There was something very satisfying about putting those two women together.