In the biography of Kate Buss it states that her sister Annie joined her later but I think that she was already in America.
Annie left her husband , Caleb Stephen Waite, who was a watch repairer and habitual criminal in prison when she left from Liverpool on 17th Feb 1911 bound for Nova Scotia. She left behind 2 young children (Phyllis Maud Waite was cared for by Kate's parents). She crossed the Canadian / American border on 26th Feb 1911 with her destination being Lydia Frances Ballestro ( nee Laurence) in Van Buren, Arkansas who was a friend from Halling, Kent. This means that she was already in America when Kate boarded the Titanic