How much weight loss is too much?

I've been trying to find this answer everywhere but it just won't turn up. People say if they start loosing weight, then it's time to worry, then people say that a little weight loss during a fast is okay depending on the snake. During my girl's current winter fast I just want to make sure this weight loss is okay.

She was at 1400 now she's at 1300.

I wasn't too concerned at first, but now that its reached 100 i'm not too sure. She hasn't eaten since the end of November.

Temps are 80-85 with a 90 hotspot. Humidity is fairly low at 20-30 but i have a humid hide that she goes in frequently thats at 70. I measure with a temp gun and the acurite thermometers

More than 15% body weight is when I intervene, which would be 210g for your girl. But pay attention to body condition though, 15% is just a rough guideline. A long skinny girl will get into trouble fasting a lot quicker than a short, fat, girl even though they both may weigh the same amount.