The usual suspects are the Bose QC 35 (now QC 35 II), Sony MDR-1000X (now WH-1000 M2) and Sennheiser Momentum 2.0 wireless. Bose have the best noise cancelling, the others will sound a bit better. I would add the Sennheiser PXC 550 as they fold a bit flatter than the Momentums which is why I picked up a pair for travel. Look into those four pairs and pick the best balance of features and sound for her use.
No worries, great to hear Bose has some serious competition on the NC front. How do you compare the sound quality of the Bose and Sony?