I think you're worried about nothing, honestly. Young snakes are typically fed once a week but now that your BP is 1.5 years old, there's nothing wrong with
feeding her every 2 weeks. That's what snakes do when they grow up: they eat gradually bigger prey at longer intervals (unless they're wild, then they have
to contend with what ever they catch and whenever they can catch it). Not seeing your snake, of course, but a snake that's on the "lean" side is apt to live
longer & be healthier than one that's a little pudgy, and they don't lose weight easily (who does?) so be glad. I personally would only offer food every two
weeks at the most, and never when she's in shed, and not worry one bit. Have you been sizing up her prey a little? See chart below:
https://ball-pythons.net/forums/show...ing-Guidelines