Complex sentence: A pregnant girl under the age of 18 may ask for an abortion without consulting her parents first if she accompanied to the clinic by an adult of her choice, who must not tell her parents or any third party about the abortion.
Split into simpler sentences: A pregnant girl under the age of 18 may ask for an abortion without consulting her parents first, but she has to be accompanied to the clinic by an adult of her choice. This adult must not tell her parents or any third party about the abortion.