She uses the first.
Maybe, but it isn't up to her. There's no need to deviate from Standard English just because the word already ends with an 's'. Basically, write what you would say: "Truss's", pronounced "Trusses", is not hard to say, so why not write that?
The first use of genitive is considered to be standard English. As far as I know, all English proper names ending in -s take an `s when the genitive is needed : Dickens`s novels. If we take into consideration foreign proper names as Cervantes, Euripides, Sophocles, etc., we have to add only an `[ apostrophe] in the genitive:
e.g Euripides` works.