If she has an ID showing she lives at your address, yes. When you go to pick up her AP, you will need to present your
DVC Member card and ID and she will need to show her ID with your address on it.
Yes. You cannot modify an ADR online. However you could try booking the same restaurant again online with the larger number of guests. If there is availability, grab it. The booking system will pop up a message that you already have a reservation for that same time and will ask if you want to cancel the original. Click to confirm and the old one will be gone.
If there isn't availability for the larger group, then call to see if they will modify it for you.