Car Accident- Do I legally have to pay for damages to a friends car?

A few months ago I was driving my friends car because he had begged me, since he had his licence suspended. Whilst driving the car, another car in front of me braked suddenly at a set of traffic lights (in the rain) which caused us to slide into the back of the vehicle. In Australia, you are pretty much to blame if you rear-end a vehicle and I was fined by police for %26quot;Following Too Close%26quot;. My friends car was insured and I also have insurance on my own vehicle, however, I am unsure of how everything is covered with me driving his. Anyways, my friends mum decided to not claim on his insurance because apparently it would have been %26quot;written off%26quot; and instead straight away paid roughly $2500 to get his car fixed privately as she was unaware that he didn't even have a licence to drive the car. Now she is endlessly hassling me to repay her this money when I hadn't had the chance to agree to prices or sign any sort of agreement, I didn't even get the chance to get quotes on different repair prices. I was willing to pay the excess if my friend made an insurance claim, but I really cannot afford this when I have my own things to pay for. Do I legally have to pay back this money? I am responsible for the accident, but now I am feeling really ripped off by what they have done.
Car Accident- Do I legally have to pay for damages to a friends car?
I would talk to your insurance company, and your friend's insurance company about this. It may even be worth talking to the police, or to a lawyer or ombudsman.

Because your friend's mum chose to get the car fixed herself, then you should only really be liable to pay for the excess that you would normally have had to pay off your friend's policy.

How did the other car get fixed? Surely there should have been a claim, anyway?

If you have already paid the excess to get the other car fixed, then you should not be held liable to get your friends car fixed privately, as well.

Unless it was only covered by a third party policy, and not comprehensively insured.

If the car was insured by third party insurance, then I assume you would have to pay the costs of repairing the car. But if it was comprehensively insured, the excess would have paid to get both your friends car, and the car you hit repaired.
Car Accident- Do I legally have to pay for damages to a friends car?
She lost all legal recourse when she refused to go through her insurance company. You could have been found liable for any excesses not paid by insurance, but that is all.