Dear Rene, I think  you handled it just perfectly, until she could tell you
herself.  This is such a huge blow to the parents and they have to accept
it at their own pace and in their own   way.  It must be so hard for them
to tell  others that their baby is less than the perfect newborn they had
expected.  And she probably didn't even know it could affect his suck.
Bless you for being so gentle with her.  Sincerely, Pat in SNJ