In fact, the whole Epilogue seemed like a piece of fanfiction that a fifteen or sixteen year old might write. Better grammar and more coherent writing of course.. but you could probably do a quick Google search and find hundreds of similar Harry Potter endings out on the web.
As a former HP fanfiction writer myself, we worked really hard to try to make our stories fit her world as much as possible, to predict or fill in where she had not yet written. So if the ending reminds you of fanfic you’ve read, that’s less because of a flaw in JKR than because of talented writers :-)
I had the same reaction to Snape’s memory scene in “Order of the Phoenix”. I wrote fanfiction about Harry’s dad and friends at school, as did most of my fandom friends, and I would have sworn one of us had written that scene in a story somewhere. Heh.