It isn't Julia Baird, it's the other one, Jackie. Jackie Dykins - Julia's full sister, daughters of the bloke the mother shacked up with but didn't divorce Lennon's dad. The one further up is the half sister who was put out for adoption, being the daughter of Julia senior and some bloke while Lennon Sr was at sea. Her name at birth was Victoria but her adopted name was Ingrid Pedersen. John learned from his aunt Mimi about her existence and tried to find her but looked in the wrong place, wrong date of birth and didn't have the new name so he never met her. She met Yoko but Yoko was off with her (similarly, Yoko gave the house that the other two half sisters lived in when they were young which John bought but never put in their name, Yoko gave that house to the Salvation Army even though she knew John wanted the girls to have it. Bah.)
Have to say, both of Lennon's Dykins-half-sisters look very like their mother.
I'm not making this a question as Yoko isn't a musician (and I'll maintain that opinion) but I thought I'd add a pic since I'm talking about women on the periphery of the Beatles ... Yoko's first child, Kyoko Chan Cox