I would have expected a longer letter, with more offers of help, and reassurances of love and validation of Harry's needs, in addition to the guilt-tripping, had Petunia not been narcissistic.The letter comes across as controlling (I raised you to be X; you must be X). You may be right -- Petunia may have stopped herself from writing a longer letter, after reasoning about it -- but I am skeptical because she doesn't seem to be that subtle in her interactions with others. I'll be interested to see how Harry and Petunia interact in the future.