Seems the basic issue is too much contrast between black and white flooring and grays of shower? The flooring would be what i would consider changing. What does your mother like least? Need more photos of whole room to be of more help. For example if vanity was black with marble top this would help integrate the look. Then fluffy white towels with black shower step out rug and other accessories it can come together. Don’t give up.

Here is photo that might help.

Rejoice! You get to have a complete do over. Because there is not a shred of waterproofing in that wet area. It’s done so improperly that it has to be a joke. Because he is using a lippage management system. What kind of tile guy knows enough to manage lippage with a system but not enough to waterproof properly???

Hire a better contractor next time. This one is a cheap hack that needs to give your money back and move along. Buy him a TCNA manual as a parting gift. He needs it.

https://www.tcnatile.com/products-and-services/publications/218-english-publications/188-handbook/957-2018-tcna-handbook-for-ceramic-glass-and-stone-tile-installation.html

How to not get snookered again.

https://www.ceramictilefoundation.org/homeowners-guide-to-hiring-qualified-tile-installer