That's a ridiculous theory. If you buy bonds in your daughter's name, they are hers -- period. You made a gift at the time of purchase, not when the bonds are cashed.
Let me give you an analogy that might help make this clear: If you buy 1000 shares of Microsoft in your daughter's name, have you made a gift? Do you have to wait until she sells those shares (which may NEVER happen, by the way) before you "made a gift"?
If you are co-owner of the bonds, the BEST argument that you can make is that you gave her HALF the value, but even that is weak if her SSN is used. Keep in mind that you CANNOT buy the bonds yourself because you reached the $30,000 limit. Only your daughter can buy the bonds. So she bought them, but they are really still yours? Come on!
The law in this area is clear as day. Anyone who wants to pretend otherwise is welcome to do so, however.
Bruce