I think that you always need a script. I can't find anything explicit saying "You must have a script", but the assumption just seems so implicit. You have stuff like:
or
The virtue granted is always the one from the script.
And so forth.
Plus it would be really unbalancing to get a virtue with no risk.
But more importantly, I don't want to backpedal on Terra's injuries, so could we at least say she was trying to make one?
Lets rule it thusly:
She has to at least attempt to make a script (with at least a +1 bonus), or use an existing script
failure to make the script is irrelevant, barring story events or disasters, the script is unusable but you still initiate.
I believe the rules were written with the assumption that nobody would have an effective skill high enough to initiate without one, but it does say repeatedly if your score I not high enough you may use an initiation script.