I went ahead and called the spa and got the answer to my own question. For anyone else that's interested in the answer...
AP holders get 10% off weekends, 20% off weekdays (DVC members get the same).
And they said only the passholder/member gets the discount - you can't "gift" it. Though I'm not sure how that would work - I've made an appt for a service for DW in the past and paid for it. I would think if I did the same (I pay for it) that I would get the discount???