I agree with you completely-her comments are secondary canon to me. And when she says something that I truly believe is refuted in the books or seems came out of thin air I give it less merit. For example she wrote on her website that DD died in 1996 and on that next-gen family tree that Fred died in 1997 and has never corrected either error (as far as I know).
Regarding DD/GG, there are subtle hints of it in the book-how Grindlewald 'inflamed' him or whatever. And the way Elphias Doge speaks of Dumbledore, he sounds as if he was infatuated with him.