You're already heading toward the inevitable, so I'll help ya along...
Get her a wonderbra, and buy her a consult with a plastic surgeon. When she opens the gifts and gives you that look that lets you know she's on the precipice of either delighting in your well-though-out humor or killing you, just tell her that she's starting to sag and you want her back at her perky best. If you have a chance, you might add that if this works out, you'll even spring for the cost of doing something about her bellybutton next birthday!
