When you say locked up at night, where do you leave her? I would suggest crate training her, and give her a bed in a crate, with newspaper at the other end. Most dogs do not like to soil their beds, but as this has now become a habit, it will take some time and you can gradually reduce the paper area and increase the bed. At least it will be confined and easier to clean up.
Try feeding her in the morning so she has longer during the day to get rid of it, but do this gradually over a few days so she is not left hungry by not being fed one night.
Just a biscuit before she goes to bed will help her to settle.