Kaley, who plays waitress Penny in the comedy series, told ET Online that she understands why some people might think it's too fast but to them, it's absolutely right.
"From day one I just knew immediately and it's been magic. We have all the same family friends," she explained. "We grew up with the same people, we just never met. So I kind of feel that I've known him my whole life. I know that it seems a little crazy on paper, but it's what works for us."
Kaley added to Rocsi Diaz that she wasn't expecting a proposal as Ryan had thrown her off the scent by picking a fight in the morning before he popped the question.
Naughty… but clever!
Kaley and Ryan confirmed their engagement just days after making their red carpet debut as a couple at the Emmy Awards in Los Angeles.
It's been a pretty amazing couple of weeks for Kaley, who is also celebrating the return of The Big Bang Theory to US TV this week with its highest ratings ever!
She tweeted: "Thank you to all The Big Bang Theory fans who turned in last night giving us the best ratings ever. You are why we do what we do."
And, as if an engagement and stellar career weren't enough, she's also very much the proud big sister right now as her sibling Brianna has been wowing the judges on the US version of The Voice.
Viewers of the US reality show saw Kaley cheering on Brianna from the sidelines last night as she attempted to win over judges Christina Aguilera, Cee Lo Green, Adam Levine and Blake Shelton.
Brianna performed Lady Gaga's 'You and I' and got both Christina and Cee Lo to turn their chairs around. She chose to join Christina's team.
More stars who are engaged in our gallery below:
Copyright: Instagram Mark Wright