There are many reasons why a wedding guest—who cried at your ceremony and danced at your reception—doesn't end up giving you a gift. What to do? First, get an idea of why it happens, then figure out how to handle it.
Reasons for the Non-Gift
The most common one is that she's under the impression she has a year to buy. This handy "rule" has no basis in reality and was most likely thought up decades ago by someone who was short on cash. By the time your one-year anniversary comes around, though, the non-gift-giver figures you've got everything you need already so why bother giving a gift? Or they simply forgot.
Another reason is procrastination. While the wedding may be uppermost on your mind and you've got a packed to-do list, a guest has lots of other things on her mind—work, school, family, and other obligations. So she keeps putting off buying you something and suddenly the wedding day is here and she's giftless. Too embarrassed to say something about it to you at the wedding, she vows to send you a present as soon as you return from the honeymoon. But then she, too, promptly forgets.
Gifts also get lost in the mail. The only way to know if one of yours is missing is if the giver asks you if you received their gift. The tipoff: You didn't send a thank-you card.
Should you say something?
No. Since there's no obligation on anyone's part to give you a gift, you shouldn't confront them—even nicely—about their "omission." It's a situation that happens to plenty of brides, some of whom still send a "thank you for coming to our wedding" note. It could come across as being passive-aggressive but in many cases, the brides (and grooms) are truly thankful the person came to the wedding and was part of the celebration, gift or not.