Unfortunately, love just isn't enough. Love does not conquer all. If someone mistreats you, then your quality of life is going to be in the toilet, regardless of what love may reside deep in the heart.

Do you think you could cope with being alone? Fear of being alone often motivates people to stay in unhappy relationships.

Going through with a wedding, IMHO, would be granting her license to treat you as she does. Why should she change, if she can get away with staying just the way she is?

A deeper problem you have is a tendency to be tolerant of someone you see as more domineering than you. If her being dominant means you don't have the means to resist her, then you are pretty much at her mercy. Her tendency to be overbearing is probably not something she can change, or would have the least desire to change. You are doomed to victimhood, if you believe that you can't possibly prevail against someone who is more assertive than you are. Either you have to assert yourself (which could mean a lot of friction in the home,) or you have to leave or you have to be mistreated. I don't see a fourth option.

I think it's a phantasy to hope that your fiancee could be counseled into becoming nicer to you. Not when she is satisfied with being how she is. She sees you as the one who needs to change. In a way, she's right. The dynamics between the two of you won't change, until you change something. You're the one who is dissatisfied with the status quo.