Harding v Hinchcliffe, 1964 - Moving motorcyclist overtakes bus on B-road going past junction to minor road, bus was indiciating to turn left into junction. Motorcyclist collides with car pulling out, turning right. Car 100% at fault, as should have checked to make sure the road was clear
Clark v Windchurch, 1969. Very similar case to yours, with the motorcyclist being found entirely at fault, however this case differs on key point - the moped driver hit the front bonner of the car, which showed the car was crawling out slowly - as you hit the side, clearly the car pulled out too fast without checking properly
From what you have said, I think you should be looking at 100% in your favour, maybe settling for 80-20.
Filtering is legal, you were not undertaking. As such, the onus is entirely on the car driver to make sure the road is clear before pulling out. Even if a car has stopped for her, there is no law in the UK that means that she now has right of way, she must check to make sure the road is clear, and as you were there and she didn't see you, that's clearly her fault.
However, you need to be able to prove you were not going too fast to be able to stop in time. I think what I would likely argue is that based (perhaps on the Clark - Windchurch case?) that as you hit the side of her car, but causing very limited damage, she clearly did not "edge" out but came out fast without checking the road was clear, and that you clearly could not have been travelling at a very high speed else you would have caused considerably more damage?
Seriously though, I'd ring White and Dalton - I've seen them win dozens of cases over the years that other solicitors would have just backed down on through not knowing road law, and motorcycle specifics!