the problem with helphire is specificly with the costs it puts on the industry
Helphire only take on cases where they are sure that you are not to blame and there is no way you could be at fault. Given that you were already on the roundabout, and she drove onto it, into you, this looks like just such a case.
The problem is that they will charge her insurance co something in the region of £200 a day for your hirecar, so thats £1000 a week. If your car is away for 2 weeks then thats £2000 plus the actual cost of the repair, which being insurance work is usually extornionate anyway. As an exmaple, i bumped into the back of somebody, cracked my numberplate and scratched her car.
Helphire charged my insurance co £700 for a new bumper fitted and sprayed, and over £2500 in hire car charges for 2 weeks (who needs 2 weeks to fit a bumper)
Total cost to my insurnace co = £3200 for a scratch
Total cost to me = £10.
This wont pose you a problem, as its not you who picks up the costs. But its companies like helphire that cost the insurance companies millions in un-needed charges. They are effectively profiteering out of the insurance companies
which puts our insurnace premiums up.
Now they've got involved its too late to turn back, so dont worry too much.