I suspect a lot of people claim their dogs never showed signs of aggression in order to excuse their own negligence.
If your son has educated himself in the ways of a discontented pitbull, and take steps to prevent bad habits from forming, that dog will be fine.
I highly reccomend getting involved with a pitbull owners group, if there’s one nearby; I learned alot from more experienced owners!
Does she look like a pitbull to you? She looks like she could be a mix to me but I am not an expert on Pits.