"a guardian can't sign for her"
Hmmmmm? That's a good question - and I don't know the answer.
The only clue is that I have been discussing taking out policies on my grandchildren [a policy they can cash in at 18 - to use for college]. Their parents would have to consent and sign the policies - but that's a parent-child relationship (and they're all under 18). So .. I don't know if the same thing would apply to a guardian.
And .. it might differ in certain states - although I think most insurance regulations are intra-state.
Even if a guardian could have signed for Terri - she would not have been able to pass the physical - which I believe is an insurance regulation "must have". Once a person has that major a physical limitation - I don't know of any insurance company which would be willing to take the risk; and "risk" is how people are rated - what is the risk she will live a reasonable length of time.
This is a great question - and I wish some insurance person would answer it.
It is quite possible that Terri had a policy before the accident.
From what I have read, she worked for an insurance company, didn't she?