By looking at the last pic, there are clear approach lanes to the r'bout, even though there are no marking actually on it, still means each driver has to go 'around' the r'bout and not over it. Alot of these have some form of CCTV, try your local council who may be able to help you with that info.
She is obviously a lazy female driver who only thinks mirrors are for checking lippy in!
Just one thing I dont understand is that the lanes are staggared at approach so she would have been infront of you when stationary or did neither stop at approach?? As she crossed lanes she is at fault and i'm sure Mr/Mrs x can be found as a witness!!!!
Dont have anymore contact with her, as the guys have said, leave it all to the Ins. companies but give them FULL details, read and re-read to make sure its clear what you are saying, get your lane descriptions right, dont leave yourself open for picking at, then fight it! With an excess like yours, you have to!!!
Out of interest was it day or night?? Also were there any other vehicles on the r'bout at the same time, ie slightly infront of her or by her?? Just wondering if she had to move over (not saying shes right!), just curious.
Looking at that top pic again with road alignment, she must have started to cut across before getting on the r'bout, kind of how your lines show, anyway, good luck!
Hope you get sorted, good luck with it, but take no sh*t