The other thing that makes me think it's not 'spy' is what comes before: 'I did not think that I was hampering myself with a...' —hampering yourself with a spy would be a strange way to put it, as opposed to being endangered/undermined/betrayed by one. It makes me feel better to know a poet mentioning this in a serious book couldn't figure it out either...!

(Surely if it was anything beginning with SH, she'd write 'sh---' rather than 's---'—anyway...)