I think most of this kerfuffle is the awkwardness of verbiage in Texas law which does not comport with what most people understand to be the norms in law.
I've also pointed out to Bubba Ho Tep that the definition he quoted of Texas statute doesn't seem to have any provision for people who shoot and kill people for lawful reasons. (Like protecting their own life.)
A straight reading of it asserts that anyone who kills anyone for any reason is a "murderer", and that is clearly not correct factually.
The definition of murder (including the “intentionally or knowingly causes the death of an individual”) is in Title 5, Chapter 19 (Criminal Homicide) and the exceptions to it are in Title 2, Chapter 9 (Justification Excluding Criminal Responsibility).
All the standard exceptions are there. You can use deadly force to protect yourself, others, your property, and other people’s property. (And plenty of other exceptions).
This just came down to whether or not it was reasonable for her to believe that she was in her own apartment.
If she reasonably believed that he had entered her dwelling with force, then she was justified in using deadly force.