It was her own wish fulfilment that put Ron and Hermione together, that's how I understood that interview, and I don't think she regretted it as such but she acknowledged that it probably wouldn't have been the best fit for either of them long term. (But I hated the way that interview was reported in general and think a lot of the articles skewed it incredibly). The epilogue of Harry Potter was written very early on, by the second or third book IIRC. I think it would have been better if she'd just kept that as ideas of which characters would develop relationships within the story, rather than them all having happily-ever-after marriages with their high school sweethearts, which seems a very simplistic idea of love. I think her knowledge and understanding of relationships has greatly grown and changed since then, it's brilliant the way she writes all the relationships in the Strike books.
Looking forward to a new Strike. I only really understood IBH on the second re-read. It was brilliant how the online world was created, absolutely spot on, but it was quite boring to read through.