It is funny that knowing the location and likely complextion of the lady even now I cannot see any noise worth bothering about ... but then I started with film where unless working with MF or LF noise [ grain] was an accepted fact of life and the real question was/is does it detract from the image. Certainly here it does not.
I suspect flash would have spoilt the image so your caution in picking high ISO paid off ... though unless you took more than one frame I think you would have had the shot before she noticed the flash. But then she might have been upset at having her picture taken. Judging from a shot my wife took with her Ipad thingie recently I doubt if her shot in the low light would be as successful as yours Tejal