Was it stated in her profile that that's a clause of the power?
Nope, last time she used it it applied to everyone. I think the name is meant to imply that only that person should be affected, and that should mean that it would work as long as they understood that it was them being addressed.
I'd compare it to one of the stronger Servant resisting a Command Spell, maybe. It seems like that sort of situation.
Yeah, I think that is a reasonable comparison.
The thing is that this is pretty much an excuse for you to do whatever the fuck you want without penalty. The eyes are basically just something for you to use and make the RP go the way you want.
In short, bullshit.
There are ways around it, though. For example, don't let her look at you. She's in a wheelchair....
I agree it is quite powerful, but I suspect that the power is reduced because whenever someone seriously contests what she's saying they'll just bullshit some excuse not to be affected by it. It also can't force you to do anything strongly against your principles.
Oh, BTW, Arch, does your vampire speak Japanese? Because Kiyoshi sure as hell doesn't speak English fluently, and he certainly wouldn't be speaking it with Rin or anyone else in his family....