Coming into this discussion late, I have to agree with Tank. When in doubt, rewrite.
But I'd like to make a few comments:
In the first case, although it is not technically a double negative, the sentence structure is built implying the negative. (much in the same way that certain words build in the conditional like "if". In many languages other than English, the double negative is the right construction. That's why I think that the sentence sounds right to Anna.
In the second sentence
She wondered if perhaps she hadn't dreamt the whole thing altogether.
what confuses me is the "if perhaps"...and ..."whole thing altogether" which are both redundant. The sentence makes perfect sense simply as: She wondered if she had dreamt the whole thing.
Often, the simpler the sentences, the clearer they are. You know, the KISS principle.
Just keep writing away, Lynn. I'm looking forward to reading your next work.
gerry
