Hi Debbie and welcome.
Your hamster is getting to be a middle aged hamster now and will start to show signs of aging. One of these is weight loss and as long as she seems to be eating well, drinking and is still bright and active it is just one of those things. From about one year they do tend to age. There is an article here you may want to take a look at.
http://www.hamstercentral.com/wiki/The_ ... y_Hamsters
We start supplementing food with our oldies. The teeth do not work as well and they enjoy some softer food as well as normal hammie food. We give porridge, baby food, scrambled egg, chicken, cooked pasta,rice pudding, tofu, cheese and cooked veg as well as raw fruit and veg. Only give in small amounts like say a teaspoon a day. I am sure she will appreciate these.
A little debittered brewers yeast sprinked on the food can help her coat.
Keep a close check for any lumps or bumps, drinking and weeing a lot, swollen tummy, discharges etc and see a vet if any of these are seen.
The front teeth look large in a hammy but they do have a few smaller grinding ones too.
Otherwise enjoy her retirement years and treat her as normal with some extra cuddles and tasty treats.