In Root A, Takatsuki does seem to be fascinated by Kaneki's name, but,
I didn't at all expect her to be the One-Eyed Owl.
I just looked her up on the Wikia and it says that
she is the One Eyed-Owl as well as the horror novelist.
Is this true only in the manga or is it also true in Root A?
Yes, it's shown clearly in the anime that
Sen Takatsuki is the One-Eyed Owl.
They started giving hints about it in first half of the episodes in Season 2.
Season 2 Episode 1
Kaneki joins Aogiri and is welcomed by this girl named Eto
Eto seems to like Kaneki
Season 2 Episode 2
Later on in the next episode, Eto removes her bandages and smiles while taking Kaneki's name
Season 2 Episode 3
In the next episode, we see this author Takatsuki and she smiles the same way as Eto while hearing Kaneki's name - Can safely infer that Takatsuki is actually Eto
Season 2 Episode 7
The same smile pattern after hearing Kaneki's story from Hinami. Takatsuki is Eto confirmed!!
Season 2 Episode 11
I think you missed this part. It was shown after the ED theme in Season 2 episode 11. It clearly shows that Takatsuki is the 2nd Owl, and the only daughter of Yoshimura (who is also called non-killing owl)
She seems very interested in Kaneki, so it seems very likely right away that she's someone in Aogiri. Moreover, it grows more and more suspicious as the season continues, especially when you notice that when she interviews Shinohara and Juuzou, she tries multiple times to ask about whether it would be possible to create a ghoul via the transplantation of organs and seems much too interested in the subject for comfort.
Her interest in the subject makes sense if
she is the one-eyed owl, because as a half-ghoul, the one-eyed owl would try to dig into the past of another half-ghoul (i.e. Eyepatch), were one to show up. One-eyed owl would naturally be interested in the subject of half-ghouls, meaning Takatsuki fits the bill perfectly.
