For a woman with a height of five feet and two inches, normal weight is 53.07-56.70 Kg or 117-125 pounds. Age is not needed to calculate weight after 18 years of age. If you are overweight then try to reduce by taking care of diet and bringing lifestyle changes.
I would say nothing less than 50kg if you don't want to look too thin, to about 56kg, but remember muscle weighs more than fat so you could way a bit more and still look slim and toned if the weight is from muscle. I'm 5ft 2, very petit and small framed, uk size 6-8 and I currently weigh around 52kg. At my biggest I got up to about 60kg and lost the weight eating a calorie controlled diet and doing pilates. Once you understand the relationship between food, energy and fat its not very difficult to spot why you put on weight and how to manage it.