"Normal" depends entirely on the individual snake. What you want to track is their personal relative weight. Are they gaining? Staying steady? Losing? Have they had a sudden drop in weight? Gaining weight is normal for a young snake, obviously....very desired. Some snakes gain weight slowly...some more quickly. Losing weight beyond what they lose when passing waste or eggs is always undesirable, but sometimes unavoidable.
You don't have to weigh her food....but it helps to learn how to eyeball a rat's weight in grams. Some people are really picky about feeding very specific amounts of food. Some just eyeball sizes and call it good. Just know that if you frequently feed rats that are too big, she may eat more sporatically or quite eating altogether for an indefinite period of time until she remembers to get hungry again.Woah woah woah, slow down a minute, I didn't know I had to measure/weigh her food!! What's the the "same width as BP at widest point" method?? I've fed her rats that were a bit fatter than her and she ate them no problem. Is there really a big deal about the weight and size of her food?