Emily's Quest by Lucy Maud Montgomery

Emily Starr and Teddy Kent have been friends since childhood, and as Teddy is about to leave to further his education as an artist, Emily believes that their friendship is blossoming into something more. On his last night at home, they vow to think of each other when they see the star Vega of the Lyre.
As Emily grows as a writer and learns to deal with the loneliness of having her closest friends gone, life at New Moon changes. Mr. Carpenter, Emily's most truthful critic and favorite teacher dies (warning Emily, even as he dies to "Beware --- of --- italics."). She becomes closer to Dean Priest, even as she fears he wants love when she only has friendship to give. Worst of all, Emily and Teddy become distant as he focuses on building his career and she hides her feelings behind pride.