We have a more expensive AC unit right outside our bedroom. It is very
quiet. We normally have the windows closed when the AC is running, so
I can't tell how loud it would be that way.

When I am outside, the most noise is made when the unit kicks in.
Other than that, the fans in the HVAC inside the house make more noise
than the AC outside.

I have brick and insullation between me and the AC, as well as double
pane windows.

With the windows open it is possilbe that the sound is resonating in
her room.

As previously mentioned, larger shrubs provide good sound buffering.
Make sure there is no reflective (sound) surfaces nearby. Make sure
the AC, if it is sitting on the ground, is level and on solid footing.


Or how about moving your AC, if that is an option?

Just some ideas.