EXCLUSIVE: 'RHONY' Star Luann de Lesseps Reveals Why She Forgave Her Fiance

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Luann de Lesseps is moving on. The Countess has dealt with discussion of her fiancé, Tom D’Agostino Jr., all season long on The Real Housewives of New York. On Wednesday night’s finale, she was given the news that he’d kissed another woman at a hotel bar just days after proposing. But, she didn’t break things off – she told ET why in an exclusive interview at her home in the Hamptons.

“We love each other,” she says. “I always say if you can't forgive the people you love, then who can you forgive? … I'm not going to let a silly kiss ruin the rest of our lives.” De Lesseps says the kiss “of course” made her question her relationship at first, but that speaking to D’Agostino made her see things differently. “If he was trying to hide something would he really be in public? In the middle of the Regency Hotel? Kissing somebody?” she says. “I think he was just being stupid, and people make mistakes.”

The RHONY star says the key to moving on was knowing her fiancé regretted his actions. “I think the key is to know and believe that someone is truly remorseful and somebody truly made a mistake, that there was no premeditation,” she says. “I think it was not premeditated -- I think it was a silly move and something that he feels really terrible about, and that meant really nothing to him.”

EXCLUSIVE: Inside Luann de Lesseps' Glamorous Hamptons Home!

The two are currently planning their wedding for this New Year’s Eve, which is D’Agostino’s 50th birthday. De Lesseps says she knows they’ll be together for the rest of their lives, and that today, she trusts him “totally.” She’s looking at wedding dresses, preparing to send out invitations and finalizing the guest list. De Lesseps says co-star Sonja Morgan will definitely get an invite, but the other ladies might or might not.

“I’m still working on my guest list,” she says. “This is the most exciting time of my life, getting married again after all this time. I am thrilled. I am not going to let what has happened on the show ruin the most exciting time of my life.”

EXCLUSIVE: Bethenny Frankel On Telling Luann de Lesseps About Her Fiance's Kiss: 'I Wouldn't Do It Again'

De Lesseps will be confronted with her relationship again on the show’s reunion specials; part one premieres Aug. 31 on Bravo. The reunion taping was explosive, but de Lesseps says she found "redemption" in it. "You get to really tell your side of the story," she says. "I personally like it because there's redemption. There's starting over."

To find out why the RHONY reunion might mean Bethenny Frankel won’t return for another season, watch the video below.