Do you mean you don't want to work the line or you are not allowed to work the line?
Have you been in the same place for 12 years? Some more information about your situation would be helpful to give you a better reply.
I want to work the line and have been a dishwasher for 12 plus years. My boss hired new people and she put them on the line .She put a worker on the line that has been there for only 6 months. When he started he was a busser .
Ask her what you can do to be considered for a position on the line. Ask the line guys what you can do to help them out on prep jobs, restocking the line items, and things like that. Watch them at work and learn what they are doing as much as possible while staying out of the way.
Start talking to chefs in other restaurants and explain your desire to learn and grow in the profession and to move into line work. There are plenty of chefs out there that are looking for people that have a good attitude and work ethic.
Also doing this, because chefs talk to each other, word might get back to your boss and help change her thought process on moving you into line work. A damn good dishwasher is an employee you don't want to lose because you are too short sighted to see that they could also be a damn good line cook!