Re: relactation, how does it works?
It's never too late to start producing milk again. The way is works is that stimulation to the breast by a nursing baby or a pump sends a signal to the pituitary gland, which then pumps out a hormone called prolactin which causes the breast to produce milk. So any time a mom desires to make milk or to make more milk, what she wants to do is to nurse or to pump frequently, aiming for 8-12 times in a 24 hour period. If the baby will not nurse, the mom should use an excellent pump, preferably a hospital-grade rental with correctly sized shields. She should also be patient. Getting a milk supply back means investing a lot of time and effort!
It sounds like you're really interested in relactation- but how does your sister in law feel? This can be a really sensitive subject for a lot of moms, so I suggest approaching this very gently. Your SIL has been through a lot, and she might not feel like investing more time and energy into breastfeeding.
Coolest thing my big girl said recently: "How can you tell the world is moving when you are standing on it?"
Coolest thing my little girl sang recently: "I love dat one-two pupples!"