I understand the OP's concern at being required to sign a document which was possibly over-detailed and unnecesssarily legalistic. However she should not take it personally. This was a commercial relationship and whilst she is no doubt honest, a number of the shipping line's customers will not be. If they had handed her back her passport without her having signed the promissory note, she could have simply walked away without paying. The company has procedures in place to protect itself against that possibility. Bear in mind that the purser would probably have been held responsible for any shortfall, and would not have the authority to amend the document or circumvent the procedures.

The document seems rather heavy-handed. Unlike Richard, I'm not a lawyer so I can't comment on whether the document needed to be in the form it was or whether the simpler format suggested by the OP would suffice. However I have seen enough American legal documents to know that they are even longer and more complicated than their UK equivalents.

The OP was in an unfortunate situation, and there appear to be other issues as well. However the ship was not obliged to extend credit to her at all - they could have insisted on her paying in cash.

I don't think the ship was unreasonable in its request, although the form of the document may have been unsatisfactory. However I am surprised that they did not require her to sign it before running up any further expenses - she would then have had a chance to object and perhaps make other arrangements. In any event, since she had every intention of repaying the money immediately it seems to me to be an entirely academic concern.