You cannot claim your girlfriend as a dependent unless she lived with you for the entire year. If she was in prison she was not living with you.
Also, you are nowhere near 100% of her total support, or even half of her support. The prison provides housing and meals, and probably clothing. All of that is part of support. The money you send her is a small part of her total support for the year.
The bottom line is that you cannot claim your girlfriend as a dependent.
