I hit someone and no damage to me but 2 dime size dents?

I hit her and she got my info but I didnt get hers is that bad. since it is so small she wants to get an estimate (it's just a plastic bumper) and have me pay so we don't have to go through insurance. does any one know price range it's an Infiniti ex35 and the rear bumper is messed up in 2 spots. I don't want my parents to know should I tell them I'm 17 and no damage to mine. So what should I do please walk me through. The lady I hit was very nice and understanding so should I just wait for her to call with estimate