There's a video where she and Daniel Radcliffe are having a conversation about the Harry Potter series while they were filming the last movie. Daniel brings up Dumbledore being Gay, and why it wasn't in the books. Paraphrasing, she knew he was Gay from the start, and his sexuality had no baring on Harry's story, so why flaunt it. She mentions that in Half-blood Prince the Movie, she had to nix a line that Dumbeldore says in the beginning about being attracted to a young lady. Paraphrase qutoe, "I wrote on the script, and handed it back, No... Dumbledore is gay, he wouldn't say this."
She also admits she told, Alan Rickman that Snape loved Lilly, and it would eventually come out.