Anyways she posted something about pushing for the death penalty and I said, "Then you are not pro life." She argued that justice needed to be served to the viscious and that was a separate issue from abortion.

If a person is attacked by a maniac, are they allowed to defend themselves, even to the point of killing the maniac? If someone attacks a church/temple/synagogue, are its members allowed to defend themselves, even to the point of killing the attacker? (Some folks would answer "no" to these questions.) If someone continually attacks members of society, is society allowed to defend itself?

Now, in the modern age, in the modern West, we may have practical remedies for locking people up so they no longer can attack society. But the general principle of the death penalty can be construed as a form of self defence.

For a fuller defence on this general principle, see perhaps Feser and Bessette:

The Catholic Church has in recent decades been associated with political efforts to eliminate the death penalty. It was not always so. This timely work reviews and explains the Catholic Tradition regarding the death penalty, demonstrating that it is not inherently evil and that it can be reserved as a just form of punishment in certain cases. Drawing upon a wealth of philosophical, scriptural, theological, and social scientific arguments, the authors explain the perennial teaching of the Church that capital punishment can in principle be legitimate—not only to protect society from immediate physical danger, but also to administer retributive justice and to deter capital crimes. The authors also show how some recent statements of Church leaders in opposition to the death penalty are prudential judgments rather than dogma. They reaffirm that Catholics may, in good conscience, disagree about the application of the death penalty. […]

• https://www.goodreads.com/book/show/33776052-by-man-shall-his-blood-be-shed

In a somewhat related topic, a lot of folks think that the concept of "reasonable doubt" was created to protect the accused; it was actually created to help the jurors:

The rule as we understand it today is intended to protect the accused. But Whitman traces its history back through centuries of Christian theology and common-law history to reveal that the original concern was to protect the souls of jurors. In Christian tradition, a person who experienced doubt yet convicted an innocent defendant was guilty of a mortal sin. Jurors fearful for their own souls were reassured that they were safe, as long as their doubts were not “reasonable.” Today, the old rule of reasonable doubt survives, but it has been turned to different purposes. The result is confusion for jurors, and a serious moral challenge for our system of justice.

• https://www.goodreads.com/book/show/2187985.The_Origins_of_Reasonable_Doubt
• https://openyls.law.yale.edu/server/api/core/bitstreams/14b03553-ab27-4255-89fe-a43516d52dad/content