try to give her less food and exercise more..
I just adopted a 3 years old plus female lab.. She's fat like a pig when I first saw her, she can't even jump up when she wanted to welcome us. But she's now getting slimmer and slimmer(after staying with us for about 3 weeks plus), and now she can jump on people (although it's not preferable by most of the people..
). What we did is that we bring her to climb hill daily, and give her less food. It works well for her, I don't know whether it will work for you or not? Yeah, I give her Addiction Zen Vegetarian right now, about 180g per meal (one meal daily). I know it's very little food for her, but until now she's still ok and healthy.. I'll give her more kibbles after she goes back to her normal weight. she's still overweight now, but we stop bringing her to climb hill this 2 weeks cause my other female lab is in heat now..
so, didn't bring both of them to climb hill until everything is over.