That she didn't include many servants or other working class people in the plot in her novels I think is partly a question of style. She just didn't write that kind of novels. She doesn't say much about them in her letters either, but all this doesn't prove that "she didn't see them,or that they were invisible to her". With her sensitive perception she must have been well aware of the injustices of life. First naturally of her own family's situation relative to those in the upper classes. Remember that most of the families the Austens associated with were a step or two above them,economically or in status.
But I'm sure she also realised that she was priviledged compared to the lower classes.
And how did she cope with such a situation. As most of us when we don't want to deal with something unpleasant,she probably surpressed her feelings. From being aware of the class system in England at that time to wanting to do something about it,there is big step. Jane Austen wasn't the kind of person to take such a step. Particularly considering her family background and her restrained role as a woman. And as I mentioned in my last post, her religious belief might have induced her (conveniently) to leave those bigger questions of right or wrong in society to God.
I'm convinced though that we could find enough proof in her letters or novels that she was a person with a conscience.

But why do we want her to be so good? Why can't we allow her to be a little bad? I think I prefer that.

Leif G-n