Can you feel her ribs ? or her hips ?
On a dog you should feel the ribs but not see them, and you should not be able to feel her hips, If you can not feel her ribs then she should loose some wheight but the best thing to loose wheight is excersise, you dont have to put her on some special food if she is a little too fat just walk her everyday then it should go away soon
If you can feel little bit of the ribs then she is fine !