I doubt she’s the only one ever. The Knave seemed to at least care a little about Ana - which was buried beneath a lot of betrayal. Hers is so much more intense because Regina has always felt everything like a body blow, but I doubt that she’s the only one ever much as Snowing isn’t the only case of TL ever.
wouldn’t be the first time one of us fell for our secretaries, would it?
"I know you, and you feel things, deeply. With or without it you feel things with your whole soul.”
You feel things deeply, and with or without [your heart] you feel things with your whole soul.