Hi there and thank you for the question. I am a Registered Nurse and will be happy to help you today.
Honestly, to keep yourself from being locked in to one arena, I would go through a general NP program and then concentrate on Psych when you graduate. This way you will be much more rounded in different areas of NP and you can build upon your knowledge and skills. While the online Psych NP sounds interesting, I still think a general NP would be a good foundation. However (there's always another side of the coin), if time is a factor and you are 110% sure you want to be stay with Psych, then sure - you could always do the program offered at the University of South Alabama.