I feel like generally you would have a large framed mirror that spans the full vanity -

@la_la Girl I agree... or move the cabinet to the counter top and hang a light fixture over the sink with a small mirror centered on the sink.

I’m not suggesting these mirrors, just showing the concept, but you can treat the space as if there were two sinks and do two mirrors. I think your light fixture is a little awkwardly sized and placed for just one sink, so I’d be lookonk to change that, whichever mirror configuration you choose.