Police: Oklahoma Mother Arrested After Shooting Man She Found In Daughter’s Bedroom

There is another part of this that was not addressed in the article, and that is aspect. Did he have his back to her so that she could not see who it was. In which case, from a legal standpoint, shooting him would be dubious at best. Self defense goes away when the person against whom you are defending yourself is retreating. The real problem with this whole scenario is that it asks one to balance the raw emotional response to finding a much older adult sneaking out of your teenage daughter's bedroom, and the legally permissible response to an unwanted person in the home.
As a parent defending one's child is at the forefront. Sometimes that means defending them against their own stupidity. That can only be taken so far before it causes such a rift that the relationship between the parent and child become irrevocably damaged. At that point, the parent has to allow the child to fall on their face.
As a citizen of the United States, we live in a nation of laws where each individual (theoretically) is subject to the same laws. The man crawling out the window has rights under the law.
So the emotional response is that the bastard should have been shot right in his dangly bits so that they are no longer distinguishable from hamburger. The legal response is to call the police, have him informed that he is not to return to the property, make him sign a summons acknowledging that he has been warned, and then when he returns he goes to jail.
I personally like the emotional response better.

Hopefully she neutered him by shooting him in the cajones...

I wouldn't hesitate or lose a night's sleep. More important was how was this 16 year old raised to be doing this in the first place. The mother may be justified, but has fault in this case, one way or the other.