Well... I guess I can finally talk something related to them with real info and not just by using speculations.
About Netmarble:
For the moment I have to assume that this character, Tioreh, will be canon in other Nakaba's projects. Netmarble has never before added by itself an original character
which lore is part of the universe of NNT/4KOTA; they have only created characters for their own original universes (Ragnarok and 7 Seven Catastrophes). And all new characters related to NNT universe that they added in Grand Cross first were designed by Nakaba himself. And later it seems they were added in the manga recently (Galand's nephew as example).
And knowing Netmarble was also in charge of the last NNT movie, whose Part 1 coincidentally has Diane looking for their children in the FKF, it's practically a fact that Netmarble is aware King and Diane have children, scheduled to appear in the sequel; therefore they would not risk the veracity of the NNT/4KOTA lore regarding the characters with "Oh yeah let's create an OC character and.... yeah let's say she's King&Diane's daughter". Not when the author himself confirmed 2 years ago that they will appear in 4KOTA. Everything would end up being contradictory.
Conclusion: I assume Nakaba is behind Tioreh's design and lore and collaborated with Netmarble to make her a main character in 7DS Origins, while she will also appear in the sequel when times comes.
About her design:
According to some recent Q&As a friend sent me, we got to know more about Lancelot’s transformations as a half-fairy being.
Q97: Amagawa: Are Lancelot's transformation enchanted with the transformation targets' abilities (flight for a Fairy or superhuman strength for a Giant)?
A: Yes. The abilities he gets from transforming are on a high level than a genuine Fairy's.
+ another Q&A where Nakaba said that
Lancelot can't fly while being in human form and so on.
With this, a Fairy/Giant hybrid must work in the same way. They can have a giant form (which I assume they can be big and strong) or a fairy form in order to move easier and be able to fly.
Let's not forget that Lancelot has multiple fairy forms, and in all of them his appearance is very modified. He changed his size, his skin colour, his hair colours etc.
So before someone asks
"But why Tioreh has pink hair?!", we have to remember fairies are shapeshifters. Therefore it's very likely the Tioreh we see now is just her Fairy form and her pink hair is just part of her transformation.
I wonder how she would look like in her Giant form.
And leaving her hair aside, her face is literally Diane's but with eyes close to orange like King's, I love it. No wonder Hawk recognized her quickly.
And she wears a sweatshirt+hoodie similar to King's original one, I love how the sleeves have the same 4 squares pattern as the back of King's sweatshirt