Well , she can always look at the blockchain , and you're out of luck at this point.
And if you manage to get a separate address that she doesn't know about it , you can get also a debit card for that purpose also.
No real advantages here , sorry.
It was more meant as a joke, but yeah of course there are other ways.
Bitcoin doesn't send mail to your house like credit card companies do, but yes I get your point.