£50? Point out to her that it’s £120 or you are going through her insurance and whether or not they accept liability it’s an accident for her and very likely increased premiums when she has to declare it at renewal time.
ie, driver fobbed you off at the time and now offers ‘goodwill’ – the cynic in me says you’ll never see the £50.
Tell her it was on CCTV and you’re going to report the incident to the police, as you should have done at the time, maybe add something like that your foot is extremely painful too (but don’t tell that to the police!). I’m with davenorth1, play the game that they’ve started.
Always get details at the scene and call the police if there is fault and damage. I like to give people the benefit of any doubt but in a traffic incident that would go instantly.