Harry Potter and the Deathly Hallows
by J.K. Rowling
Affiliation: Order of the Phoenix
Mrs. Weasley is the same loving, fiercely protective, and sometimes rather aggressive mother we've known her as all along. And this woman is no normal mom – she's more like a force of nature. This sometimes makes Molly an oppositional figure (but with the best of intentions); for example, even though she knows Harry – and Ron and Hermione – must go and find Voldemort, she really doesn't want them to, and tries her best to keep them from making any such plans. However, when it comes down to it, she's also just as dedicated to the fight against Voldemort as the rest of her family is, and so her maternal instincts have to be willing to make some compromises.
The last significant thing we see Molly do in the novel is vengefully destroy Bellatrix Lestrange, who's been threatening her children for ages, and who just took real aim at Ginny. Here, we see that she's not just a formidable mother, but a powerful witch, as well. When asked how she decided to have Molly be the one to defeat Bellatrix, Rowling said in a web chat:
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 optios [sic] for Blelatrix [sic], 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, 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. (source)