What would be a polite (normal) thing to call a middle aged woman that you're not familiar with instead of ajumma?"Imo"?"Ajumeoni"?
"저기요" makes me feel like I just called the lady over so she could take my dinner order.
While the psychokaren in question is a relatively young 37 years old, she would still fall into the ajumma camp, which is the standard term for all married or 30-40+ women.
Women want to be called ajumma about as much as men want to be called ajeossi. It's best to avoid either with anyone under at least 50.
With all that being said, an office worker once called me "언니". He was a man and twice my age.
Something gender neutral like excuse me would probably do the trick. Speaking of tricks, Bruno Mars says ladies are pimps too.