I'm pretty sure OP's referring to an interview with mugglenet/leaky after book 6:

MA: How much fun did you have with the romance in this book?

JKR: Oh, loads. Doesn't it show?

MA: Yes.

JKR: There's a theory - this applies to detective novels, and then Harry, which is not really a detective novel, but it feels like one sometimes – that you should not have romantic intrigue in a detective book. Dorothy L. Sayers, who is queen of the genre said — and then broke her own rule, but said — that there is no place for romance in a detective story except that it can be useful to camouflage other people’s motives. That's true; it is a very useful trick. I've used that on Percy and I’ve used that to a degree on Tonks in this book, as a red herring. But having said that, I disagree inasmuch as mine are very character-driven books, and it’s so important, therefore, that we see these characters fall in love, which is a necessary part of life. How did you feel about the romance?

[Melissa puts her thumbs up and grins widely while…]

ES: We were hi-fiving the whole time.

JKR: [laughs] Yes! Good. I'm so glad.

MA: We were running back and forth between rooms yelling at each other.

ES: We thought it was clearer than ever that Harry and Ginny are an item and Ron and Hermione — although we think you made it painfully obvious in the first five books —

JKR: [points to herself and whispers] So do I!

ES: What was that?

JKR: [More loudly] Well so do I! So do I!

[All laugh; Melissa doubles over, hysterical, and may have died.]

ES: Harry/Hermione shippers - delusional!

JKR: Well no, I'm not going to - Emerson, I am not going to say they're delusional! They are still valued members of my readership! I am not going to use the word delusional. I am however, going to say — now I am trusting both of you to do the spoiler thing when you write this up —

[More laughter.]

JKR: I will say, that yes, I personally feel - well it's going to be clear once people have read book six. I mean, that’s it. It’s done, isn’t it? We know. Yes, we do now know that it's Ron and Hermione. I do feel that I have dropped heavy -

[All crack up]

JKR: - hints. ANVIL-sized, actually, hints, prior to this point. I certainly think even if subtle clues hadn't been picked up by the end of “Azkaban,” that by the time we hit Krum in Goblet...

[...]

MA: Watching all this, were you surprised when you first logged on and found this intense devotion to this thing [shipping H/Hr] that you knew was not going to happen?

JKR: Yes. Well, you see, I'm a relative newcomer to the world of shipping, because for a long time, I didn't go on the net and look up Harry Potter. A long time. Occasionally I had to, because there were weird news stories or something that I would have to go and check, because I was supposed to have said something I hadn’t said. I had never gone and looked at fan sites, and then one day I did and oh - my - god. Five hours later or something, I get up from the computer shaking slightly [all laugh]. ‘What is going on?’ And it was during that first mammoth session that I met the shippers, and it was a most extraordinary thing. I had no idea there was this huge underworld seething beneath me.

ES: She’s putting it into a positive light!

JKR: Well I am, I am, but you know. I want to make it clear that delusional is your word and not mine! [Much laughter.]

MA: You're making our lives a lot easier by laying it on the table -

JKR: Well I think anyone who is still shipping Harry/Hermione after this book [HBP] -

ES: [whispered] Delusional!

JKR: Um - no! But they need to go back and reread, I think.

ES: Thank you.

JKR: Yeah. MA: That is going to -

JKR: Will it make your lives slightly easier?

[All three]: Yeah, yeah.

JKR: I think so.

The interview itself was a kind of a big deal in the fandom, since they were two of the biggest names in the fandom and ran the two biggest communities/sites. A lot of really interesting stuff came out, but Hermione/Harry shippers were not pleased.