When you find yourself trying to remember a show (or any works) that's on the tip of your tongue but just out of reach, come here - the collective brain of the TVTropes community can probably help. Post all the details you can remember (examples help). If you're looking for a trope, head over to Trope Finder. Have general questions about tropes? Visit Ask The Tropers!
This seems the most like you described: https://tvtropes.org/pmwiki/pmwiki.php/Literature/GriffinsDaughter
I didn't see anything about the goblin who was immune to AIDS or the shape-shifting children, so maybe you mixed two stories up? It tends to happen a lot :/
Nope, I already checked that one earlier. Griffin's Daughter is definitely not it.
The human parts takes place in modern times (or at least the 80s), for one. Also, the cover is completely different, though that's a minor observation.
I don't think I'm mixing two stories up because everything was tied together in one way or another. F'ex, the goblin revolt? Established in the very first chapter, when it's mentioned that the MC's husband's family was horrifically murdered just before the story begins and their goblin security detail was nowhere to be found afterwards. The bodyguard assigned to the MC? Turns out he's the former goblin king, but he was overthrown in a coup d'etat around the same time.
I distinctly remember that the blurb on the back of the book was about the shapeshifting kids, even though the book turned out to be more about setting up the goblin revolt thing. It's the reason I read the book in the first place, because I was sick of Chosen One farm boy fantasy stories.
The kids turned out to be really important, as at the end of the book, the mermaid child saves the fairy world because the siren song can jam radiowaves or something, while the elf woman *finally* has a normal elf kid with the half-goblin because it turns out elves can't have true elf children. Because that's logical. But nonetheless, the fact that every elf is basically half-elf was supposed to be a huge plot twist.
Dunno if this helps, but I think it might have been written in 2006 or 1996. I remember looking it up when freaking AIDS became a plot point, because it seemed such a dated thing to do.
It's sad how I remember almost everything about this book, except for the damned title. It's also sad how many times I've edited this reply so far.
Edited by Exagge

So there was this fantasy book that I read back in 2009 that I can't seem to find information on anywhere. It was a reinterpretation of old Fair Folk stories.
The plot follows a married elf woman and her various liaisons, namely with her bodyguard and a bisexual half-human/goblin. A huge driving point of the plot is that she can't seem to have any normal elf children; they all turn into other mystical creatures when they hit puberty (they become a dwarf, a brownie, and a mermaid iirc). Around 2/3 way through the book, her mother shows her a way into the "human" world, and the plot completely shifts to combating both a goblin uprising and human scientists discovering that the magical world exists and causing all sorts of chaos with their experiments.
I'm almost positive that the title of the book was sort of like "Jelenda" or something, but my Google-fu brings up nothing (or just Valkyrie Profile results, which is not this book!) The title was definitely the name of the main character nonetheless, and the cover was a really pretty digital painting of her. She was white and had a brown braid, and I think she was wearing a nightgown.
Help me out, tropers?
Edited by Exagge