Alright, I have a question about the wording of Sansa's response. It reads:

After a player plays an attachment on Sansa Stark, that player may draw a card.

The wording of the response makes it sound as though opponents can draw cards through this effect in addition to you. However, my understanding is that responses are optional unless otherwise stated, and may only be triggered by the card's controller (again unless otherwise stated). This response does not include "may be triggered by any player" or any other such text. So if an opponent plays an attachment on her and I do not wish to trigger the response, what happens? I believe that they would not be able to draw the card, but I'm not 100%, so I figured I'd ask before it actually comes up in a game.

You are correct. Only Sansa's controller can trigger the Response. So Sansa's controller has to let an opponent draw a card when they play an attachment on her.

In a multiplayer game, it can be a useful bargaining chip. "Play something good on Sansa, and I'll let you draw a card."