PATRICK SWAYZE’s still-grieving widow is shell-shocked over KIRSTIE ALLEY’s sensational claim that she secretly plotted to run off with the married  star!

Heartbroken Lisa Niemi feels so betrayed by her once-close pal that sources say she wanted to scream at Kirstie: “I hate you! Patrick never loved you! How could you do this to me?”

Kirstie dropped the bombshell just as Lisa was starting to rebuild her life. She recently began dating Florida jeweler Albert DePrisco after losing her husband of 34 years to pancreatic cancer at age 57 in 2009.

“Lisa has so many happy memories of her marriage to Patrick,” said the source. “Now, Kirstie has sullied those memories by trying to cash in on her friendship with him.”

According to insiders, 56-year-old Lisa knew Patrick and Kirstie became fast friends while filming the TV miniseries “North and South” in 1985.

Kirstie was married to actor Parker Stevenson at the time, and Lisa never suspected Patrick was romantically involved with her, sources say.

But that’s just what Kirstie claims in her new memoir, “The Art of Men.” The Emmy-winning “Cheers” star, 61, writes that she and “Ghost” heartthrob Patrick tried to “avoid going down that road,” but couldn’t help falling in love.

“He exuded that ‘anything was possible,’” Kirstie writes. “The emotions and dialogue escalated daily. One night, toward the end of the shoot, I got fairly drunk, dirty-danced for hours, and then succumbed. We made out with each other.”

While the two weren’t sexually intimate, Kirstie writes that Patrick “asked me one last time to divorce my husband and make a new life with him. He was very persuasive. The decision of whether to run off with him was torturous.”

Ultimately, Kirstie – who’s now competing on “Dancing with the Stars: All Stars” – said she turned Patrick down after confessing her forbidden love to her father and him telling her: “You’re married. Knock it off.”

Still, they continued the flirty relationship until she decided that although she was willing to ruin her marriage for him, she didn’t want to destroy his marriage.

Kirstie remained so close to the couple that Lisa invited her to speak at Patrick’s funeral, and “she knows Patrick would never deceive her like Kirstie has described,” said the source. “But now that he’s gone, he can’t reassure her of his love – and that hurts immeasurably. Lisa feels humiliated. She’ll never, ever forgive Kirstie.”