I would take the paint back to the store and tell them that it is a nice color but too dark. Depending on the base they started with they may be able to help you by adding a quart or ratio of same base white. It can be iffy, my daughter has done it several times with success. The downfall would probably be you would never be able to match it again.

Hmm, I'm not sure about gray walls with the warm granite and dark cabinetry. The undertones of the granite are fighting with that Revere Pewter, IMO. I have used SW Mindful Gray with Giallo Ornamental, but it was tempered by white cabinetry and a lot of natural light. I'm not sure it would work in this case. Accessible Beige might be an option. But honestly? I might try a color rather than adding one more neutral. Your fixtures, mirror frames and granite are really nice and a color might bring them out better.

I had the exact same problem. I picked out the vanity I wanted but did not think about the fact that it wasn't made to sit flush against the wall. I spent a month looking for something else, but in the end we decided to go with something shorter and have it not be against the wall. But we were going from 72" to 60" which is probably not workable in your mom's situation. I did find a lot of vanities that did have flat sides and could work in a corner, if you are willing to have the countertop fabricated. They just need to not have any trim detail on the top or bottom like the one you picked out does. I would just look at the ones without the pre-made tops. Because the pre-made top will still leave you with a slight gap because of the countertop overhang. This is an example: Avanity Modero which is sold everywhere, not just at Lowe's. The cabinet we ended up buying is an Avanity Madison which won't work for you, but I assume it is of similar quality. We are pretty happy with it. The drawers and doors have soft close but I do feel like the glides in my Ikea kitchen drawers are better quality. It is very pretty and I wanted a stained wood so I am really happy with our choice. If I had been willing to go with a painted finish, I think we might have stuck with the 72" Modero.

The undertone of Shoreline is a mossy green. So, I would say don’t chose it. With out seeing the bathroom, I’m working with memory of the “almond” fixtures. This? I like to find a coordinate, not a match when both almond & tan cause confusion. I would paint the walls: Again, because you have posted no photo, choose the shower curtain in the same color as the tile. Choose art with a nickel finish frame and you are done!