The Lark in the Morn by Elfrida Vipont.
Published 1948.The following summary is obtained from Goodreads.Twelve-year-old Kit Haverard is the only daughter of an absent-minded, scholarly Quaker father. Along with three older brothers who are currently away at school, dreamy, untidy Kit has been raised by their young energetic cousin Laura.Ever since the death of Professor Haverard’s wife, Laura ...