It is not at all surprising that Mrs Stisted is claiming for her loss as a result of this accident - it is quite normal for any party to do so as a result of an accident of any type, and she will of course be doing so with legal advice.
What is interesting is why she is claiming against the estate of the pilot. I would have expected the aircraft insurance to include adequate public liability cover for the passengers carried. So perhaps either the insurance company are declining to pay out for some reason, or the level of PL cover is insufficient to meet the claim.
The most important thing is that particularly freelance pilots should be very clear who is going to meet any claim in the event of an accident when they are flying an aircraft. Whenever there is loss, there is very likely to be a claim, and given the % of aircraft accidents that are caused by pilot error it is no surprise that the pilot is likely to be sued for negligence. Make sure the insurance of any aircraft you fly covers you for any public liability claims. If it doesn't, maybe you can get your own PL cover. But if no insurance covers you, expect your estate to get sued in the event of an accident.
And finally let's not forget that the most important reason to make sure all documents and legislation is complied with, is that insurance may well be invalidated if it is not!
I'm no expert however, so hopefully we can see some comments from Flying Lawyer here. Assuming he's not involved.