I also think it is your SIL's duty to tell her that she doesn't want her doing what she did last year. I am sorry for her, though, that she had to go through that crap. No one deserves to be treated that way on their special day. I couldn't image people in the delivery room with me other than my husband. I am a very private person., but thats just me. So my advice would be to talk to your SIL or just leave it up to her without saying anything, but to me its her place, not yours.