You've not mentioned whether you have your own insurance. Most (but not all) insurance policies provide third part cover for driving someone else's car. If you were covered in this way, you won't need to worry about the possibility of prosecution.
When the car owner renews her insurance, it's unlikely that the accident will affect her policy. Although insurance policies relate to a specific vehicle, it's actually the driver who is insured and not the vehicle. The insurance company is unlikely to penalise her for an accident which occurred when she wasn't the driver.
However, if you have (or will be seeking) your own motor insurance, the accident will probably increase your premium.
Irrespective of whether there's any insurance cover, the law entitles anyone who suffers loss or injury, through your negligence, to claim compensation from you. Both the owner of the car you were driving and the owner of the other car involved in the collision can send you the bill for repairs and, if necessary, pursue you through the courts for payment. However, if you had third party cover under the provisions of your own insurance, your insurers will pay for repairs to the other car involved in the accident.
Both of the car owners are also entitled to pursue you through the courts for secondary losses which they incur because of the accident. (e.g. the cost of a hire car while their own car is being repaired). If you had third party cover, under the terms of your own insurance, it's possible that the other driver's secondary losses might be covered but you would still be liable to pay for the secondary losses of the owner of the car which you were driving.
If you were driving with no insurance cover at all, you should consider yourself lucky that the accident didn't involve serious injury to the other driver. If so, you could have been sued for millions of pounds.