Even slow feeder, poor feeder are generally bigger by that age not to mention 3.5 feet is really short for a 7 years old female.Pretty sure she's a female because all my females of the same age are approximately the same size. I feed sparingly and wanted to emphasize building a healthy muscular snake instead of a big fat girl. She's about 3.5 feet right now.
I am one of those people that grow their animals slowly and yet I still achieve at least 1200/1500 grams in 3 years as an average.
Poor feeder might take 4 years to get to 1200 grams.
So that gives you an idea, growing slowly is one things but again 1250 grams at 7 years that is more than slow growing even if they grow at different rate, now the proportion looks good based on weight/length but I would likely re-sex her.