Very likely somebody already said it… it is highly unlikely that people will change. And sadly, an intolerant girlfriend will very likely only turn into an intolerant wife.
Breaking up is never easy. But breaking up now will be much easier than breaking up 20 years, three kids, one mortgage and two dogs into the future.
Can you promise you will stop dressing? Of course… until the next time.
At the end it will only be a decision of you two, and the only fair thing to do will be full disclosure from both sides.