I didn't read this from the psychological perspective that people who study Freud might have. Consequently, I probably had a much better experience.
If you read the book from start to finish, believing it's true (and I don't see any real reason to believe it's not—seeming consonance with Freud's theories is hardly enough to discredit it or even arouse noteworthy suspicion, unless Freud is already known for being dishonorable; however, I'm not a follower of Freud's theories). The diary isn't all about sex, okay? Sure, Rita is curious about things she doesn't know or is in the process of learning, and she talks about them in rather secretive ways (without directly saying what she's talking about), but really, if that's all you focus on while you're reading the book, you're going to miss out on everything.
Take my advice and just read it for her sake, and yours, and not for psychology. Care about her, and what she cares about. See the good in people. The very ending might be a lot too much for some people, though (be warned), but if you care a whit about Rita, it will change your life if you do. The whole book should definitely stir emotions and feelings.
It's actually a really good book, and my favorite to date, however odd that may sound. I just found it randomly on some website, and started reading out of curiosity, but I'm glad I did.
The intro. talks about typographical errors and such as if they're rampant, but there really aren't that many at all (none to speak of). In fact, I was impressed at the writing quality for someone so young (and though it is a translation from German, I still find it impressive).
I noticed that Rita does a fair amount of ice skating in this. I wonder if she's connected at all to the Grete Lainer who was a figure skater. They're likely not the same person since she would have been pretty old then (in the 1930's), but maybe the name is a tribute or a child's name or something. Hopefully we'll be able to find out the true identify of the author some day (there should be enough information to do so, given some hard research, if anyone ever cared to try it—unless Vienna wasn't the real location, or some such). I don't know if it's far enough in the past for it to be safe to reveal all that information, though. The author's children would probably still be alive.