Urgent: Need Help With Dog Please?

I adopted my dog last year and she was pretty mangled when I got her home. She had a broken leg from being beaten so badly amongst other issues from her previous owner (T.M.I: Not Part of the Problem). To top it all of she was underfed. I put her on a regimen with her dog food where I gave her 1/2-3/4 of a cup two times a day and I was walking her often. She was at about 20lbs which was a healthy weight but now she is 30lbs and I am starting to worry because I can tell she is getting pudgy. She is an 20 month old Tibetan Spaniel mix. I want to know what I should do to get her down to a healty weight again. Any ideas? Thank you ahead of time.