You most certainly can have two names on a deed and that will put both names on the account, thereby giving you both equal access to the HGVC system. There are, however, two questions you will need to address:
1. Do you want to be "joint tenants with right of survivorship" -- wherein the share of the deceased party passes to the surviving party outside of probate -- or do you want to be "tenants in common" -- wherein the share of a deceased party remains a part of decedent's estate and passes to her heirs thru probate?
... the latter event could require either of you to deal with relatives who may prove difficult.
2. HGVC will set up a silver-tier HHonors account linked to the HGVC account. It will be a joint account, but when using HHonors online, only one name (the "primary") is used. So, which of you will be primary-holder? When booking hotels thru HHonors for the other party, they will need to add the other's name to the reservation.