What does the metaphor maria blossomed at her new school mean?

meaning becoming her own way of beautiful, it mean she is looking more pretty or getting better at something that she lack in the past.

A metaphor is a hidden comparison between two unrelated things. In this case, Maria is being compared with a flower that opens in the morning to show its beauty.

If Maria blossoms at her new school, she is happy and comfortable there. It implies that she is developing all her capacities to succeed in the academic and personal fields.