Whoreturn

To turn into a whore.

To make advances towards and sleep with multiple people despite being known for one's commitment to monogamy.

Alternatives:

To offer sex manipulatively or to exchange for pay as a last resort option.

Metaphorically speaking, to "kiss ass", to be nice to someone who has an advantage in order to gain something from them.

My ex whoreturned and cheated on me with multiple partners.

I may have to whoreturn to get a special promotion from my boss.