Grace Harlowe's Golden Summer by FLOWER, Jessie Graham

The College Girls Series sees the friends part ways: Grace, Anne, and Miriam depart for Overton College, while Jessica and Nora attend a conservatory. The Eight Originals gather on holidays, but the seven College books focus on the three at Overton, along with new friends like J. Elfreda Briggs. They form Semper Fidelis, a society devoted to aiding less fortunate students at Overton. Following graduation, Grace rebuffs offers of marriage for what she had firmly believed to be her destined work, managing Harlowe House at Overton. (Summary by Wikipedia)