Rita Skeeter's story is pretty well established from The Goblet of Fire to the Order of the Phoenix. Throughout the Triwizard Tournament she harasses Harry, eventually also getting on Hermione's nerves. As Mrs. Weasley and Harry hug at the end of chapter 36, Hermione manages to capture Rita Skeeter in beetle form unawares on the windowsill.
There was a loud slamming noise, and Mrs. Weasley and Harry broke apart. Hermione was standing by the window. She was holding something tight in her hand.
When Hermione, Harry, and Ron were traveling back to London in the Hogwarts Express, Hermione says,
"I've told [Rita Skeeter] I'll let her out when we get back to London...I've put an Unbreakable Charm on the jar, you see, so she can't transform. And I've told her she's to keep her quill to herself for a whole year. See if she can't break the habit of writing horrible lies about people."
A little less than a year later, Hermione forces Rita to write an honest article on Harry's experience with Voldemort. At this point, Rita seems to disappear from the story. The Quibbler issue comes out and sells like crazy, but there seems to be no mention of Rita until the end of the Half Blood Prince, when she attends Dumbledore's funeral.
So what happened to her between the time she wrote The Quibbler article and attended Dumbledore's funeral? Hermione said that she would keep Rita quiet for a whole year, so after that year did she let Rita Skeeter go? However, I find it hard to believe that Hermione would let Rita go voluntarily; after all, if Hermione wanted, she could inform the Ministry that Rita is an unregistered Animagus and Rita would promptly get thrown in Azkaban. Perhaps the Ministry of Magic hired her to spread propaganda and lies about Harry. Could anyone find me some in-text evidence as to what happened to Rita Skeeter to confirm if Hermione let her go or if she escaped through the Ministry's help?