Hilton will reject points credit if the name on the AMEX account does not match the name on the HHonors account. I am in the middle of this fight now. I have 50k points in my HHonors account and 95k points that AMEX cannot credit to it because the AMEX account has my wife's name listed first. It is a joint account and I have a card. Same drill if it is an account under your wife's name and you are just an authorized user.
I've just combined my wife's new account with my existing account. Amex set up a new account in wife's name when we got the card, the points from amex all went in there, even though we gave amex of my existing account number. I called amex and they blamed hilton, so I called hilton, and they dumped my points and stays into my wife's account ( because that account had a fast track to gold offer, ( 6 stays in 90 days) and 2500 points for each of the first 4 stays...
Evidently your mileage may vary, in any case, all the points are in my wife's account now, and when I reserve rooms online, the default ( which the website won't let me change) is that the reservation and folio ends up in my wife's name ( even though she has no stays of her own @ all)...
3 stays since we combined the account, when I check in I just tell the desk person that my wife made the reservation and no worries...
@ some point I may start another account in my name and try to dump the points back to that account, ( if they do another 5/10/15 type promotion) - I'll be doing enough stays this year to make diamond more than once anyway...