A claim is a claim regardless of blame, regardless of cost and regardless of whether protected no claims bonus was in force at the time. Even if the claim was made under a different policy, you as a driver have to declare all claims you have had. So even if a claim was under your company car policy or whilst you were a driver under your friends insurance it still has to be advised to your own insurance company.
So in respect of your friend the claim MUST be declared, although some insurers will only take into account claims within the last 3 years, some will want to know about claims within the last 5 years, but it still have to be disclosed. All claims can affect the rating of the policy and therefore can result in additional charges.
Failure to disclose information can result in a policy being withdrawn, this not only goes for accidents/claims but convictions, modifications, basically all information and should any information change during the course of the insurance you must notify the insurers immediately.
In some situations changes can result in the policy no longer being acceptable to the insurers, which means insurance being cancelled, you don't want to find this out after you have had a claim and the claim be thrown out. In your friends case the information resulted in an additional charge being paid, if the information had come to light after a claim had occurred the insurers may of not honoured the claim due to 'non-disclosure', which could of been very costly for your friend, plus a No Insurance Driving Conviction.
She should also advise the insurers that the policy was protected at the time of the claim, so she didn't actually lose her no claims bonus.
In respect of the actual protected no claims bonus side of things I would recommend she read the appropriate section in the insurers policy wording/policy booklet regarding how this works, as all insurers are different and you should check the scale with any potential new insurer as well. Basically the easiest way to try and explain it is think of Protected No Claims Bonus as 'lives' and in the event of a claim you 'lose a life'. Protected No Claims bonus should be transferrable from insurer to insurer, but they don't all offer the same amount of 'lives'. I don't really want to go into discussion about how each insurers Protected No Claims Bonus works, as like I said they can be different, but you must bear in mind that insurers don't have to honour protection offered with another insurer.
Hope this helps
Regards
Sarah