Across the Blue Mountains - this actually has three characters, but can be be sung by a male and a female voice.

"I'll buy you a horse, love, and saddle to ride
I'll buy myself another to ride by your side
We'll stop at every tavern, we’ll drink when we’re dry
Across the Blue Mountains go my Katie and I"

Then up spoke her mother, and angry was she then
Crying "Daughter, oh dear daughter, he's a married man!
There's young men a-plenty more handsome than he
Let him take his own wife to the Allegheny"

"Oh mother, dear mother, he's the man of my own heart
Wouldn't it be a tragedy if we should have to part?
For I'd envy every woman that I'd ever see
Cross the Blue Mountains to the Allegheny"