Karin,
I run into this all the time at the WIC office. I too find it sad.

1. I respond as quietly and gently as I can, "Is it fair to *this* child to
feed him/her something *so inferior* when your older child got all the
wonderful benefits of breastfeeding?"
2. Ask her *how* she thinks bottle feeding is going to give her more time
with the sibling. Remind her of the time spent fixing and cleaning bottles.
3. Be sure to remind her why its not OK to prop bottles that bottle feeding
takes two hands but breastfeeding leaves one had free to help her toddler.
4.I also go through the list of practical hints for dealing with two, and
suggest that the first child will learn great parenting skills by watching
Mom nurse.
 But my personal opinion is that parents who sing this song are actually
feeling ambivalent about having a second child and haven't figured out yet
that they can love them both just as much, so they are afraid to give their
all to the new baby. You keep trying. Some parents do listen, especially
when we tell them the truth even if it will make them feel guilty.
Positive (and wet) in Oregon
Laurie WIC Certifier and BFSP