Hello Rafiq,
Chickens are very social creatures and like friends so if you can get a second hen it would be a good idea.
Unfortunately the garlic is unlikely to solve this. Garlic is good for the intestines but apart from that I’ve never heard of it as a cure ... more of a healthy extra.
I would try to increase her proteins, perhaps with some tinned cat food which hens seem to like. Only give it to her for about 15 minutes a day for about 4 days. Make sure she always has fresh cool water and that the food is fresh. Avoid the fruit for a while as sugar can be a problem in excess.
If you have only recently opened the new food perhaps another bag ? Just an idea ?
Good luck