It depends on the email systems you both use whether you get confirmation of her having read your mail.
Wait a couple of days, then phone her and ask if you have sent the email to the right address.
If she says she hasn't received one from you, ask if she has checked her junk or spam folder, as you sent her, because if you have made a mistake and sent her gift to a total stranger, you want to try cancelling the gift token.
Please don't just feel offended. She sounds a buy woman, was at work all day, and it is to be hoped that your son was waiting with dinner made, or dressed to go out, or to bed with her when she got home on her birthday!