A mirror over the sink would be too low to reflect an adult’s face! Add a backsplash up to the window sill to protect the wall from water splashes. You could also add a glass shelf.

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I saw this thing on a design show (may have been property brothers) where they had an awkward window over a sink, and they actually created a bracket so that the mirror hung in front of the window. I don't know if it would work in your space, but maybe something to think about? It looked amazing in the end.

You can mount some doble mirror (normal view in one side and augmented in the other) with arm, in the left wall at face level. Search for one bigger

Pardon, at left of the sink

I can found different solutions here in Houzz: one big table mirror, others pendant from ceiling or window trim, attached to bars, etc:

More:

And:

Thank you everyone! The bathroom got sidelined as we had all our end of school activities, but I finally got back to it and decided to do this:

There will be a narrow table below the mirror soon.

And here's the rest of the room:

I still need to put the faces on those shelves & stain them.

Thanks again! The ideas I get here are so helpful!!