Possibly underweight?

[VultureTim]

Based on the pictures she doesn't look underweight at all. She looks great, actually.
When it comes to snakes there are far too many variables to determine age by weight, but 422 grams is pretty small for a 2 1/2 year old BP, especially for a female.

Body structure is more important than weight though. And her body structure looks really good from what I see in the pics.

It's a relief to hear that she looks reasonably healthy. It's hard to tell what her actual age is because her length and weight so i'll never know for sure.
After reading up on other threads and websites I started thinking she was a bit under a year old. Hopefully she's a good eater and she'll start to grow a bit so I can know more.