I really don’t think Regina knows who Emma is. If she had any inkling that the one to break the curse had made it too town, I think she would have had a much stronger reaction. She is suspicious because Emma is a stranger, but I don’t think she has put two and two together yet.
So here’s a random thought…obviously Regina remembers everything from Fairytale land. So what exactly happened when the curse was first enacted? Did Regina have to learn how to function in our world? How did she learn things such as how to drive a car and how society in our world generally works? I also wonder if she had the chance to visit our world prior to the curse through the use of the magic door room. Has Jefferson helped her get to other worlds?