Q – Why the match-up between Molly and Bellatrix [in the final battle]?
JKR’s A – Molly is a very powerful witch. Anyone that could raise Fred and George must be powerful. But sometimes that fact gets lost because her skills — like magical cooking, which is much harder than it looks, as I tried to show in the tent scenes — don’t draw much attention. But I wanted to make the point that just because a woman dedicates her life to her family, doesn’t mean she’s not highly skilled and talented and powerful. And I liked the idea [o]f paring Bellatrix’s obsessive, disturbing love for Voldemort with Molly’s maternal love. The theme of maternal love, and how being loved gives you power, was important to me throughout the books.