Correction 1:
Her name is Sakuya Izayoi.
If it was Sasuke she might as well be a warrior. ZUN chooses his characters' names according to ability and/or affiliation.
And no, she's not necessarily evil, albeit she is Chief PAD Maid to a devil. (Vampire in reality.)
Her eyes during her dialogue with Reimu/Marisa do indeed turn red, and so do Youmu's. Sakuya's eyes also turn red during casting of certain spellcards in the fighting games.
It has not been explained why they do so.
Some doujin/fan claims label her as evil, but that's mostly for fanservice.
Touhou 1-5: PC-98 Touhou >6: Windows Spinoffs: Windows
Internet.
Run your profile in Admin mode with no restrictions.
As for now, all the Touhou games (6 to 18) are only available for Windows computers and Mac (running bootcamp). Besides this, the games 1-5 are only available for download on PC-98 computers, which were dropped due to incompatibility. I'm honestly pretty unsure over how to download games 1-5, but you can find the official games on Steam, and can buy Touhou 6 on Amazon. (make sure to look for a trusted seller)
No one is UN Owen. The name "U.N. Owen was her?" is just the name of Flandre's theme from Touhou 6: The Embodiment of the Scarlet Devil.
Nobody
5' 6" (1.68 m).
The game is free, but even I'm having a hard time locating a download link.
Resident Evil 6
Ninja Warrior - 2007 Sasuke 6 Part 1 was released on: USA: 18 May 2007
Ninja Warrior - 2007 Sasuke 6 Part 2 was released on: USA: 18 May 2007
Ninja Warrior - 2007 Sasuke 6 Part 3 was released on: USA: 18 May 2007