As a mature solo female traveler, I do want to avoid spots that are so cutting-edge trendy that only 20 to 30-somethings frequent them ...
You can always identify those by their uncomfortable seating designed to keep oldies away.
I've heard that radii at the PH is quite good if you feel like staying in.
I tend to go for Izakaya/"Japanese tapas" type places when I want a light meal on my own in Melbourne at night - there are a few in that end of the CBD/Bourke St area and lanes between Russell & Parliament