I can answer the PIN part. PIN stands for Personal Identification Number. It is for you only and only you can use the PIN for your trip. You must be the lead on the reservation so nope she can't use it.

They'll release these if they feel they need to sell rooms. So there is no real certainty whether they will offer discounts or not. However, you can book now and apply a discount if it becomes available for that room type. That's for Disney discounts.