"It's only been three months but she knows Ryan is the one," Cuoco's rep told the magazine.
Sweeting proposed just yesterday on Sept. 26 after the couple made their red carpet debut over the Emmy Awards show weekend.
Cuoco shared her excitement over the engagement on her Twitter feed Wednesday night writing:
Cuoco was engaged in 2011 to addiction specialist Josh Resnik but the two called it off in 2012 and this will be the first marriage for both her and Sweeting.
"She's never felt this way," a source told Us.
"She knows this is it. And the ring is gorgeous!"