Not sure if this will help, but I found this review of Locus of Control scales (http://onlinelibrary.wiley.com/doi/10.1111/j.2044-8295.1993.tb02495.x/abstract) by Furnham and Steele (1993) when I was doing my MSc dissertation. Obviously it's pretty old so there's bound to be some newer ones, but might be a decent starting point? I ended up using Levenson's (1981) scale in my dissertation research, but the reliability wasn't great so I can't really recommend that one to your friend unfortunately!
Thank you so much for your help. I will forward all information to my friend, and let her decide on what material to use. Wishing you all a Happy New Year!