Like BP says, a lot depends on your receiver and the headphones you select.
I checked out the manual for a Sennheiser 130 stereo wireless headphone and it does have a volume control and it plugs into a headphone jack on the receiver.
My receiver, A Denon 2802, allows the use of headphones independent of the speaker settings so I have to turn the speakers off when I only want the headphones. Conversely, if I wanted to use them both simultaneously.
But, one cannot be sure they will play loud enough for her needs without trying them.
Again, a lot depends on three variables: Your AVR, the headphones and her needs.