That's right. Annie had guessed correctly: what she wanted was Frieren's hair!
You had to remember that in the wizarding world of Hogwarts, Veela hair could be used as a wand core, and it was quite powerful, too. So Annie figured that the white hair of a certain poker-faced elf big sister might work as well—maybe even better than Veela hair?
After all, Frieren was an elf, and elves had incredibly long lifespans. Combined with Frieren's tremendous magical power, from a human or wizard's perspective, she was a powerful Magical Creature in her own right. There was no question about it!
So, since Veela hair—and even Annie's own hair—could be used as wand cores, then the hair of a powerful elven mage who had lived for over a thousand years should naturally work just fine, right?
Although she had no idea how a wand made with elf hair would perform, with Annie's exceptional craftsmanship and custom tailoring, any little flaws would be insignificant.
Really, the best option would've been to pluck two of Annie's own hairs. But since Frieren and Fern weren't that close to Annie yet—they'd only known each other for two or three days—Annie naturally wasn't going to go out of her way for them.
And now, the fact that she was willing to make two wands for them for free was already an enormous favor. They couldn't expect anything more.
And so!
With Frieren happily contributing two whole hairs for the cores and Fern providing a small part of her apprentice wand to serve as the wand bodies, and with Annie's series of refinements and guidance, it wasn't long before she had easily crafted two identical wands in the Ollivanders style.
More importantly, she had made those two wands specifically for Fern and Frieren. They were perfectly