And then you could do what I did to my baby sister (15 years my junior and
by then I had 2  daughters- her contemporaries- who were happily BFing) .
I told her if she didn't BF I'd never speak to her again!  Depends on your
style and relationship.  And my son who told his wife (from a bot fdg
family) that she couldn't have a baby unless she BF at least 6 mo.  She's
had 4 now and they've each nursed over 1 1/2 years. I do like the positive
modeling idea and at least your sil's babies got that good start.
Sincerely, Pat in SNJ