Was Titania ever human? Can you explain a little more about what an ELF actually is?

No, Titania was never human.
She was created entirely in Alvin Stag’s lab.  She does look very human, as her designers
made her in their own image, but genetically there is no human in her.  

So, one of the things when writing any kind of science
fiction is that I do a lot of research into the topics I’ll be writing
about.  The question though is how much
of that information to include in the text I’m writing.  Obviously, my primarily goal is to entertain
people, and someone with Asperger’s Syndrome I’m aware of the danger of
info-dumping on people in ways that just annoy, bore or lose them, and in the
case of a story maybe even interrupt the flow of a story too much.  On the other hand some people really like all
the techy science stuff.  I guess I want
to provide just enough actual science so that anyone really interested can go
and find out about those things themselves.

In the case of ELF’s and The Little Queen though, there isn’t
really that much to it.  Most people I
think are familiar with the concept of genetic engineering, which is modifying
and splicing and doing stuff with existing organics.  Synthetic biology is a logical progression
from that – instead of just modifying an existing thing, imagine being able to
design an organism on a computer, kind of like using the creature designer in
Spore (or perhaps a little more involved, but you get the idea).  That genome you create on the computer is
then injected into a synthetic cell and allowed to grow, in the story inside an
artificial womb, or Crystal Egg.

The Crystal Eggs and the synthetic cells are all fictional,
but in real life scientists have been able to remove the DNA from a bacteria,
mycoplasma, and replace it with a synthetic genome and the ability to edit
genes on a computer may not be too far off.
I’d like to say that these are of course simple organisms and anything
really complex like Titania, or the dog/triffid things, are a very long way
off, but who knows?  Hopefully if that
did happen, there’d be a better and less self-absorbed person than Alvin Stag
to take responsibility for it.