Edith Stein was her birth name.
There are a number of saints named Teresa so you need to be more specific.
Mother Teresa's real name is "Agnes Gonxha Bojaxhiu", as she is a nun she had changed her name to "Teresa" after St. Teresa of Avila.
Mariano's real name in the novela Teresa is Mariano Sánchez Suárez.
Teresa
Her real name was Agnese Gonxhe Bojaxhiu, but she changed it to Teresa when she became a nun.
Angelique Boyer is the answer.
Sophia is her real name.
Saint Monica
No Her real name was Agnes Gonxha Bojaxhiu
Her real name was Anjezë Gonxhe Bojaxhiu
Which Saint Francis? There are several.
Her maiden name was Agnes Gonxha Bojaxhiu. Her chosen name was Sister Teresa. When she started the Missionaries of Charity she became Mother Teresa.