Twain, 45, stepped out with Thiebaud, 40, for a PDA-packed lunch at Serafina's Fabulous Grill in NYC on Thursday with an enormous engagement ring.
"I've never seen Shania so happy," a pal tells Us of the singer. Swiss-born Thiebaud, a Nestle business executive, popped the question about two months ago in Switzerland.
Twain and Frederic reached out to one another in the wake of the stunning double betrayal, and were spotted vacationing together in Canada, New York City and Florida.
Finally, in August 2009, Twain -- who has a 9-year-old son, Eja, with Lange -- came clean about their new romance.
Writing on her official website, she called Frederic "a dear friend and true gentleman...We leaned on one another through the ups and downs, taking turns holding each other up. We've become stronger and closer through it all."
Adds the Twain pal: "She has ended up with the love of her life."
For much more on the engagement -- details on the ring and their "romantic" wedding plans, how their friendship blossomed into love, and what their exes are up to -- pick up the new Us Weekly, out Wednesday!
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