Perhaps you could center an oval mirror over the sink and add a sconce to either side of it.

You need to reside the light fixture, perhaps ditch it. Reduce trim or remove it and mud it in with no trim, could also change the window or remove it. . Raising the fixture will allow you to raise the mirror

The window will look fine once you do something about the lighting and the mirror. Like so (excuse the clumsy photoshopping) -

smaller mirror, thinner window trim (that current trim is a little dated anyway) and lose that over head lighting. It's way too bulky and way too 1985. That mirror you have is meant for an antique style set-up. doesn't go w/your vanity or your faucet.

do thinner sconces or a pendant light.or a two light over head light.

the other option is to redo the top w/new faucet and a right off-set sink.

redo the window so you have a white frame that looks like this

The sink is in the center of the vanity. The mirror and lighting is what is off set. If you can move the sink to the right, and replace the mirror and lighting, I think you will be happy.

• Do you think a corner vanity might work?
  

Otterkill. no. and not for 2K. are you kidding?

the space isn't the issue, it's what OP has crammed above it.

It was just an idea....not that particular vanity.....was actually looking for more of an L shape....

laurafhallen has the same idea that I was thinking