Mezcaal is an anthropomorphic coyote who is a bartender and the wife of Raphael in the future. She and Raph both work at a bar which appeared to be named Turtle's Island. It appears she's a tough character and doesn't put up with anyone's attitude, as she once kicked out two customers after they ignored her warning not to fight in her bar.
It is never established whether Mezcaal knows about Raph's ex Ninjara.
Since Mezcaal is Raph's wife in the future, this makes Raphael the first turtle to be married in a licensed TMNT story. Other turtles in various incarnations have had love interests, but none were married to them until Mezcaal. In the Mirage TMNT story "Swan Song", Leonardo and Radical are revealed to be lovers and soulmates. And in Mirage's "Tales of Leonardo: Blind Sight", the same Leo has a vision of another life as a samurai in feudal Japan where he has a wife and daughter.