I'm emailing a letter to a company and I'm referring to my boss and her displeasure.

Would it be 'my boss's displeasure,' boss', or...?

Thanks.

If a singular noun ends with an /s/ or a /z/ sound (spelled with -s, -se, -z, -ce, for example), practice varies as to whether to add 's or the apostrophe alone. A widely accepted practice is to follow whichever spoken form is judged better: the boss's shoes, Mrs Jones' hat (or Mrs Jones's hat, if that spoken form is preferred). In many cases, both spoken and written forms differ between writers.

i'm not sure if that actually answers your question but i'd go with boss's

Yeah, that's looking like the best way to me, too.

Thanks.