I wouldn't worry too much about looks or personality. It's unlikely that your woman will end up as a clone of her mother if she's not already there by now. What is MUCH MORE IMPORTANT is focusing on whether you can deal with your potential MIL for the next 20 or 30 years or whatever. Think worst case: What happens if she gets sick or something and moves in with you?
In my case, my wife is nothing like her mother -- in looks, personality, philosophy of life, or pretty much anything else. I married my wife because I like her looks, personality, etc, and her mother being the opposite means I actively DISLIKE her. I try to be patient and not let it create problems, but unfortunately it definitely adds tension to our marriage. Even when my MIL is blatantly doing or saying the wrong thing, if I say a word my wife will defend her and we'll get into a fight. Only my wife is allowed to say or do anything. That's just how it works, and I doubt my situation is unique.
So bottom line: It's not about what your potential wife may or may not become, it's rather about what you may have to deal with for decades. I love my wife, but looking back, I knew that my MIL was a nightmare and perhaps knowing what I know now I would have made a different decision. Think carefully before jumping in if you have any concerns.