I expect she’s around Zecora’s age; if Pony Sunset hadn’t gone through the mirror, she’d be about seven years older than the Mane Six. (Assuming ponies age on the same timeframe as humans, that is.)
My guess is that she’s on the city council. It’s a humble step towards power, but what she really wants is to be a leader, not to be powerful; the Canterlot (or San Franciscolt?) city council is as high as she cares to rise for the moment.
I’ve had a plot bunny (
not that kind of plot) kicking around for a while, in which Human Sunset visits CHS after the first movie, asking why there are rumors of
her, of all people, sabotaging the Fall Formal with a gas explosion and fireworks, or whatever it is that happened there…