hi, this is obviously a new approach by the insurance companies to come directly to your door.
they usually send a letter offering compensation quite early because its in their interest to do so.
if your sister is to claim compensation privately , then it would not cost her a penny to do so, and depending on how long her symptoms of whiplash last for, she could get anything from �800 to �2250, and also all her expenses paid for (providing she keeps all her receipts).
this is why they want her to accept the offer of �300-�500 at an early stage and settle the claim.
i know this, as i work for a claims management company who specialise in personal injury for passengers who are not at fault.
i hope i have made it easy for you to understand what is happening here, and would be more than willing to assist and help you.
p.s this is not a sales pitch, i am happy to advise you if you need.