I know you've prob heard it a million times, but it was a lifesaver for me when my son was born and my youngest step-daughter was really afraid our relationship would change (adult perspective), child reality she physically hung on me, trying to sit in my lap while I nursed, and glared at Caleb every chance she got.
It helped a ton to include her in the care. We got her a dolly and had "Mommy" chats about baby care and she helped with everything. Like this, "Andy would you throw my baby's diapers away, I'll hold yours for a while, so you can get a rest." "Thanks babe, I don't know what I'd do without you".
The upshot of it is, I really don't know what I'd do without her help. She fetched binkies, tossed diapers, gave goodnight kisses, arranged blankets in the back seat of the car and held emergency bottles while I drove...