How long would a bullet would take to heal?

Well since you described in your book it was a through and through she was shot most likely with a fully jacketed .40 since its the ammo for a glock 22. Since she is healthy and athletic her body may heal quicker than most. It also depends on if it gets infected. Best case scenario it heals within 3-6 wks with no infection or complications and no need of any therapy. If she would have therapy, complications (bone, muscle, ligaments), infection ect it could take up to 3 months to heal.