Thanks, Mamzelle. I am sure there are grammar Nazis who will weigh in on your side. That said, I chose to use “distrustful” as it implies someone disengages from trust with deliberate lies intended to mislead. “Untrustworthy” implies someone can be simply unreliable — cannot be trusted to tie their own shoes, or show up on time, or fulfill their promises... but perhaps you distrust my linguistic judgement?.... It won’t be the first time I have been caught gaffing while writing.
Well, I went back and read that sentence several times. I was a pro at this at one time, and uncertainty of meaning always catches my attention faster than spelling. It isn’t a grammar problem, but a usage one. The sentence is grammatical as is.