Verbena37
Roundabouts in the UK vary so much that we can not predict the markings on the OP's roundabout... however generally speaking they are designed to share priority around the roundabout and across all junctions - so it would be rare to have a situation where dual lanes coming in at 6 o-clock continue and exit at 12 o-clock - lanes will normally go in a radial fashion around the roundabout - meaning that lane 1 (the outside lane) will continue around to 3 o-clock, then on to 6 -> 9 -> 12 -> 3 -> etc. That means that to get from lane 2 (OP's lane) to the exit involves crossing lane 1.
There are exceptions where there is a significant difference between 6 & 12 being major roads, and 3 & 9 being minor roads, but we have no idea whether that applies here... also spiral roundabouts / magic roundabouts and a million other options 
Have a look e.g. at the M4 roundabout junction 15 - randomly picked :) at the point of each exit there are no lane markings - the lane markings are only used where there are traffic lights - so who has priority when one person wishes to transition from the A346 to the A419 (6 - 12) and another comes off the motorway and realises they are a junction early so goes back (3-9)? neither has priority - equally the white markings coming off the M4 west bound show the left two lanes as left and straight on - the right lane as turn right - yet with almost no exception that middle lane will be the left of the two lanes of traffic turning right, so someone in the right lane expecting to end up in the left of the two exit lanes on the A419 will have a shock and probably be run over by a bus or lorry!
www.google.co.uk/maps/@51.5763668,-1.7325608,216m/data=!3m1!1e3?hl=en
travel on down the A419 and take the second roundabout (A420 junction), as you go under the A419 to turn right up the A420, both lanes could exit - two lanes and two lanes on exit, so comparable to the OP's situation - yet:
- both lanes also go right, left lane as well
- there are no road arrow markings
- the right hand lane (lane 2) has to cross a dotted line to exit, lane 1 does not have to cross any dotted lines to exit up the A420, OR to continue around in the way described by the OP. If the OP's roundabout is like this then she is actually in the wrong and the claim could go 100% against her!
So the roundabout situation may well not be as you show on your diagram - it is quite normal for both lanes to simply be concentric circles meaning that the OP would be the one crossing the lane line, not the other driver (perhaps the OP could link to Google Maps to show the roundabout).
Your comment though is telling: "Suddenly, the other bloke decided not to go into that exit and carry on going right. As she was already turning though, he hit into her." so which one changed direction?
ref. reactive / predictive - sorry, while I agree that you can not predict someone pulling out at the last moment unexpectedly, you can allow for the fact that they might and have an option available - i.e. go slower / give more space - that is how you are in fact meant to drive.
If someone suddenly pulls out and overtakes into your lane - might you have spotted ahead of time that they were close up behind the car in front of them / could you see them tailgating / had they approached that car fast / do you see the start of their move / are they sitting centrally in the road / what car do they drive - lots of clues, and yes you should as a driver be analysing exactly those things - the fact that you don't will in your scenario be a contribution to the accident - you could slow down and leave more space / you could speed up and make sure you are visible so they don't overtake / you could sound your horn to make them aware that you are there - several options...
And yes you can predict it - we all know that it happens at times - every car coming towards you could have a tyre blowout / the driver could have a stroke / they could skid on diesel / lots of innocuous things could happen to cause them to hit you - of course, none of us are perfect, but we are meant to be considering these things - the reality is that modern drivers are in a little safe cosseted cocoon, in their own world with the heating on / music playing / chatting to their passengers and in reality totally unaware of whatever else is going on around them - relying on luck and some misbegotten sense of 'right' being on their side to survive - sorry, but we are driving vehicles of over a tonne of metal at a fast speed, we have a responsibility to be awake to any possibility and to actively choose how we drive...