Ramona Singer, 57, accused her husband Mario Singer, 59, of cheating on her with personal fitness trainer Kasey Dexter, 32.  Although a humiliated Ramona drew up divorce papers she was considering taking Mario back... until this happened.

Bestie Sonja Morgan Also Slams Ramona Singer? 'You Couldn't Handle My Life, Singer!'

A shocking letter with an ultimatum from Mario's mistress surfaced, according to Wednesday's Radar Online. The RHONY star received a 2-page emotional letter that was published in In Touch Magazine on April 23, sharing their affair. The ultimatum: either Ramona leaves Mario or Dexter does.

The letter details that Dexter wanted to "move on, [but Mario] reminds me of how good our sex life is. I know you probably don't believe me, but I was under the impression that Mario was leaving you. The day you served him with divorce papers, he came to my apartment -which he was paying for- and took me to dinner. I love him, but do not want to continue to be involved unless you are of of his life. If not, I'm going to let him go. You and I have both suffered tremendously."

The letter also reveals that the connection Dexter shares with Mario was an instant flame: "Within days, we had an intense sexual relationship. I had no intention of hurting you."

Even after Mario returned home, Dexter wrote, "we never ended our relationship---ever. Even after he moved back home to you, he was speaking to me."

Bombshell after bombshell drops as Dexter claims that Mario professed his passionate feelings to her on a daily basis:

"He told me he loved me every day. I don't think we ever fought except when we were in Boca and you texted him during dinner." She may be referring to the Boca trip where she was screwing with him.

In an earlier April 2 Radar Online report, Mario and Dexter shared 40 texts about how much he missed her: "I'm missing your lips and eyes and laugh and [expletive]".  A source also reports they didn't use condoms during their last romp in Boca Raton, Florida.  Appearantly if Dexter gets pregnant again, she's not aborting it. All this, before Mario returned home to his family.

Ramona Singer's Stinger Stings Again

It is interesting to speculate why Dexter even submitted this steamy letter to the news, but the real question is: Will one of these ladies kick Mario to the curb? (Or both of them?)

Tags: real housewives of new york city ramona singer Mario Singer Affair Kasey Dexter Bravo