Now, if I started any sentence to my mother with the word "woman," I'm fairly certain I would immediately regret it. If I didn't on my own, I'm also certain that my mother would make certain that I did. Mary avoids the argument altogether. She doesn't even bother replying, but tells the servants to do what Jesus says, putting Jesus firmly on the spot.
This is one of the many reasons that Mary is so often called upon by Catholics to intercede for them. She is the one to nudge Jesus to help in the affairs of the world. She knows what He is capable of doing, but also how to get His attention. In this case, she knew the importance of weddings to everyday people and so pushed Jesus to not just help this one couple on this most important of days, but to make His first public miracle one that supported marriage (and the partying after).
And she got to show off her son, just as any mother would want to.