I agree with Michifus, 10 lbs doesn't seem that bad, even if she is just 11 months old.
My 3 cats are all domestic short-haired cats, but they're each built differently and therefore each weigh differently. My oldest cat is 17 years old and weighs probably 9 pounds, my middle child is 15 year old and weighs 23 lbs, and my youngest child is 5 year old and weighs 10-12 lbs. The two that weigh less are very active, while the obese one is very dormant.
Cats are better than dogs . . . they'll only eat as much as they want instead of eating everything you put out.
But there is Diet Cat Food such as Iams or Science Diet that you could try if you or your veterinarian are concerned.