Perhaps it was the low-cut dress she was wearing the first time you met her, or the fact that she used to date your son's older brother. Whatever the issue is, it's time to get over it. If you're not on good terms with your kid's soon-to-be Mrs., try to make amends.
Like it (and her) or not, she's your son's life partner, and any lingering hostility will only strain and damage the relationship between you and your boy, his wife and your future grandchildren. Even if you're all on good terms, do what you can to strengthen the bond. She's family now, so make her feel at home.