Why does Emma regret about her wedding? Have you even regreted about anything you have done?
I think that after getting married she started to think that she could have another life, full of interesting events with another man. Probably she was afraid that she had choosen the wrong man or she was afraind of starting another stage of her life where she couldn't be light-minded and absolutely free in her actions, where she should be more gron-up and responsible for another person. I think that it was her possible reaction on the streesful day.
I, personaly, try not to regret about my actions, persuading myself that what I had done was the only posiible way of acting in every particular situation. But sometimes I regret about things that I haven't done. There was a situation in my life - I was 16 and I fell in love for the first time with the boy who was elder then I was. He saw me off my house and himself suggested me to kiss, but I refused, I don't know why. I have no any reasonable explanations of this act but this is what I regret about.