Can you over feed a snake?

[marionsclan]

As my BP continues to grow, my Corn is fully grown and feeding on adult mice once a week, I will have to adjust the amount of food I give her. I am trying to follow the rule of thumb by going based on the biggest part of her body but that doesn't seem like it is enough in my opinion because as soon as she poops she seems to be 'flabby', for a lack of a better word. She still has her muscle structure and strength but she feels like she used to be fat but lost a lot of weight all at once and is now flabby (not that she was, I'm just using it as an example as to how she feels to me). Maybe this is normal, but I'm wondering if I should feed her a larger rat, she's at weanling/pup once a week right now, or should I just double up on the same size? She is around 9 months old and 2.5' long. I haven't weighed her yet, because I don't have a scale, but will get around to it shortly.