If there is a dispute over who was at fault then you need an independent witness. Unfortunately people rarely stop for accidents now (which is stupid because everybody may need a witness for themselves at some point). If there was none there and you are both not admitting liability then you needed to have taken photographs as soon as possible of the scene, leaving the cars in place. From the shattered glass and the position of the cars they probably could have worked it all out (morale - always keep a £2 disposable camera in the glovebox). To be honest don't be nice about things anymore (bitter experience), leave the cars in the position they were hit, get those photos, try to get a couple of witnesses (or car registrations if possible – if you leave the cars blocking the road you may get those details

).
I could be wrong but it sounds like from your statement ‘i’m positive’ that you are not 100% sure that it is not your fault. If you use that statement you may find you are leaving yourself open. If neither of you can prove whose fault it is then I would suggest to her that she fixes her car, you fix yours. Otherwise both of you will loose your NC bonus, both of your will have a fault accident to your name and both of you will have to pay the excess anyway.
It may also get dragged through the courts (I have a MC accident going back 2 years where the other party is making up a pack of lies and I am awaiting court procedures to try to settle it).
If you do both go and not claim on your insurance, make sure you get a signed statement from her within the next few days saying that no party is admitting liability for the accident and that each party will take ownership for their repairs to their vehicle. If you dont get this statement then you will probably need to tell your insurance as the other party's insurance will probably contact them anyway. However, you may find if you tell your insurance that they may not re-insure you the next year.
eBay can bring up the occassional bumper for around £120ish and rear lights probably fetch around £60 each cluster 2nd hand. Just make sure that things like mounting brackets etc are not damaged also.
'Who is to know what is possible until one has attempted the impossible and suceeded'