Ok lets not fall into the thinking that weight is something magical. Its simple. She gained 206 grams between 1/14 and 1/20 because you fed her between 0 and 206 grams worth of rat and she drank the rest in water. If you are claiming you fed her 1 mouse that's 54-56 grams then either she drank 150 grams of water or more likely you made a mistake on one or both of the weigh ins. If you keep records of weight on days, urinations, defications and feedings you will be able to account for all of the weight changes minus a little wieght gain from drinking and weight loss from staying alive.
You just can't get meaningful information out of changes in weight over 6 days.