"I don't have to drink. I don't need to drink. I don't drink at lunch. I don't drink with my daughter. I don't drink when I have business the next day. I wish I could say the same about some of my cast mates, because they do have to drink," she told PEOPLE at Dorinda Medley and Jules Wainstein's Real Housewives of New York season 8 premiere Wednesday at 42 West.
The 52-year-old Morgan, who only sipped water at her afterparty, explained that her RHONY cast mates have been bugging her to quit alcohol for awhile.
"What happened was that last year they caught me off-guard on camera in Atlantic City, and [the housewives] never stopped talking about it," she said. "So then, I wasn't drinking Vodka or any hard alcohol – it was just champagne and sipping wine. And that wasn't enough.
"I came back this season and they started up again with the drinking," she continued. "And I love to party, I like to get fall-down tipsy but they just wouldn't let up about it. So you know, I said, 'I'll just quit drinking and take the air out of their tires.' "
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On Wednesday, her fellow Housewives applauded her decision. "She's so much better," said Countess Luann de Lesseps. "Just a lot easier to be around."
"She's more calm," said Dorinda Medley. "Her skin looks great. I really think I've never seen Sonja looking better."
New cast member Wainstein has known Morgan socially for some time, and said her pal seems better than ever.
"She's doing amazing, and that is impressive. She's never looked better," she said. "Sonja is a strong woman and can do whatever she wants to and do it well. She's hilarious and she doesn't take life seriously, like I do."