size & age

[RB420]

is there any way to guess an approximate age of a younger snake by their size and diet?i bought my female bci in late january. i forget how old the guy i bought him off said she was, i think maybe he said 6 months. if that is right, she would be nine months old. i have fed her 1 med rat approximately every 8 days. she is about 42 inches long.

any input? I my camera is out on loan but i could probably find some fairly recent pictures of her on my computer if that would help.