I couldn't give you an ideal weight, because it seems to vary so much from individual to individual. What you want to look for is the condition of the snake. Look along the backbone. If you can see the backbone prominently then you have an emaciated snake. I'll have to see if I can snap some pictures, to give you some idea.
Also I wanted to point out that it's possible you had a full weight at 119g, and that some of the weight loss could be attributed to a defecation. You're still above where you got her, so don't panic.