She relented the fact that he was cheating her. This is a sentence giving the meaning of relent.

No, "relent" is not a noun. It is a verb that means to become less severe or strict. A noun form of "relent" does not exist.

Once Melissa felt passionate about something, it was difficult to get her to relent. The word capitulate is a synonym for relent.

He will never relent or apologize. They wanted to relent, but pride kept them from admitting they were wrong.

I will only relent when you have finished cleaning your room.