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.

I think the gray walls with a white ceiling and trim will look fine. You can reuse the mirror and have other black elements in the room ( knobs on new vanity & flooring). When we renovated our bathrooms I chose Sherwin Williams Mega Greige and it looked really nice with white sub-tiles and white wainscoting. It made the ceiling appear higher. We left the ceiling white. The tile flooring had some whites, grays and browns marbled through.

I think you will need to provide a layout including measurements to have any kind of meaningful input. That said, I would get rid of the tub because that is a terrible shower. My preference would be to have a great shower versus a tub and a cramped shower. When I remodeled I got rid of my tub/shower and replaced it with a beautiful functional walk in shower. If you must have a tub at least consider a tub/shower because it is far more comfortable to use than a small stall shower like you have. I prefered using my tub/shower combination to the stall shower in my guest bath which I used for a few weeks after an operation limited mobility. I doubt whether you have enough space to have a comfortable enclosure for the toilet but you might be able to move in to where the shower is. Depending on your budget and what lies below the floor it is theoretically possible. Whatever you do get a skirted toilet so those unattractive traps aren't showing on the side. Skirted toilets are sleeker looking and easier to get clean.

Thanks all for the input. I was sweating the black and gold and then the added nickel on just the door handle and hinges. Totally throwing me off. Have picked out so much with this house and, of all things, the hinges are the things tripping me up. You all gave the answer I was hoping and needed to hear.