Let me just say that very light exercise of the pecs may be helpful. Really any exercise at all. Heightened blood flow, especially to the area, hastens the healing process. This is also why massage works as well not to mention breaking up scar tissue.
Not sure if she wants breast massages though (there is some technique to this btw.. aiming at the pec muscles and pushing fluid towards the lympathic ducts).
Gauging what you can do from the pain is the best bet though. That's the body's way of telling you something is wrong.
But yeah, what Garrett said is true. I've read the same thing.