My oldest daughter used to sleep walk.
She, too, would be very irritable and become defensive if we tried to wake her. I spoke with our pediatrician, and he said not to wake her, just direct her back to bed... we had to physically place our hands on her shoulders, turn her around, and lead her to her bed. She never remembered it in the morning.
The scariest thing I remember was hearing someone walking around upstairs, as I went to check on the kids, I got to the bottom of the stairs and saw her standing at the top of the stairs, completely wrapped up in her bedspread. No way, would she had made it down the stairs safely, with that wrapped around her body, but... her other senses must have been working, because she just stood there, making no attempt to come down the stairs. Or, maybe I just got to her in time???
Also, with our 2nd daughter, I would sometimes find her sleeping, sitting straight up in her crib, (not even leaning on anything). I wondered if she, too, would be a sleepwalker, but nothing ever came of it.
High locks or alarms on doors are a good idea, especially if you have sliding/french doors that lead out to an in-ground pool.