I believe I do have a timeline of events that you might find enlightening.
While sharing a drink, Vanessa asks Uncle Newt questions about her parentage. She had put off asking the questions before now, even though she had her doubts for a while.
Uncle Newt is able to tell her that Susanna Noone was indeed her mother, despite Vanessa’s resemblance to Aunt Gally.
He does go on to say that Gally would have loved to have been Vanessa’s mother, and that, really, she was one of her two mothers in every meaningful sense.
When Vanessa asks what her father looked liked, Newt only says that he never met Major Noone.