Of course, allowing the 17 year old girl to kill a child under cover of law conflicts with the 14th amemdment, which demands equal protection under the law for all "persons" is each state (including Texas). An unborn child is indeed a "person."
Have you ever actually read the 14th Amendment? It specifically excludes the unborn as citizens or persons to whom the protections of the constitution apply.
"All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside. No State shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any State deprive any person of life, liberty, or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws."
The unborn are outside the jurisdiction of the Constitution. They have no more rights under the Constitution than a citizen of a foreign country does. Positive law may include protections for them, but that Constitution is otherwise silent on the matter.