I have a blended family and it was hard at first to let someone else into what I had held by myself for so long..It's hard to trust someone else will truely care and treat your child the same as their own.The dogs are just an analogy for the real question which is will you still love my child as much as "our" child.She also is tackling the question or thought of how to keep her son feeling like he's first.
Maybe you can do stuff together to help when the baby comes,say going to the store with Paul ,making dinner for the family.She will need lots of rest and helping with Paul will be a big help..
Good Luck and congrats;)