monica the second
A person who enjoys intentionally ruining relationships especially marriages by seducing the male/female of the couple. Usually this person will only go after a non single person simply for the joy of ruining that persons happiness to benefit their own. Most of the time they will leave shortly after the relationship breaks up because that was their only goal.
"Man what happened with you and John I thought y'all were tight"
"We were but some Monica the second had to swoop in and snatch him up"
"We were but some Monica the second had to swoop in and snatch him up"