The fine print is that you CAN buy and gift miles in the same year (You get 40M and your wife gets 40M), this way you would get both of the bonus miles in your account. If she had previously bought miles this year, you would be unable to make her a gift this year. If it's a 40M mile award you are looking for, your wife could gift miles to someone else (her dad?), then they would have the miles to be used for an award.