It may happen. Sometimes a bride has a vision of her wedding dress and the one her mom envisions for her is much different. You would think that the bride will win, and I hope she does, but sometimes getting the dress of your dreams can be an uphill battle.
Make mom happy by going wedding dress shopping with her and try on the style that she thinks is best for you -- you may be surprised that mom was right -- but if you still hate the style point out to her why you don't like it, and mom may agree with you once she's see you in a few different dresses.
Always remember that your mother has thought of this day probably since she was pregnant with you and is just as excited as you are that you're getting married. Indulge her a little and while I'm not saying that you get the dress she wants for you over your own opinion, I am saying to take her with you and let her know that her opinion does matter to you.
And when it comes to other details of the wedding, if there's something mom really wants and you don't really care one way or another, go with mom's idea simply because she's your mother and it will make her happy. She may back off another area of the wedding that really does matter to you.