his "parting shot" would have on her. I think he really meant well - he even told her to invite William whenever he should be back in England, which he probably knew would never occur to any of the others.

It could be, that he had been hoping she would become more lively and develope more self-esteem though time with a little encouragement. I believe he also wasn't aware of how she was really being treated by the others (except Edmund). Not because he was so careless, but because everyone else in the household was able to tarn their acts as acts of kindness. And he just didn't realize what exactly was going on with Fanny.