Thanks Succubus and rogueboy for the advise.

I was there today, and wont go again.
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I didn't particularly like her, and disliked the atmosphere there (too many ticking clocks. They made me nervous.) and during the session itself I felt uncomfortable, not just because I was nervous. I noticed the "not willing to tell certain things" thing – I told her that I was writing stories about elves, but didn't say that these elves are hermaphroditic, genderless and polyamourous. She asked if she could read the stories and while I'm usually happy about everyone who shows interest in them, I don't want her to read them. Needless to say, I didn't say anything about LGBT.
I also felt as if she couldn't really help me. Of course she did say some useful things, but while talking to her I even felt like it was absolutely useless to go even to any therapist because I could as well talk to my mum and my issues seemed unimportant, small and not "bad" enough to need the help of a therapist ...
Even before the middle of the session I had already decided that I didn't want to go to her again. Deciding that was way easier than I had thought...

So now I have to find another therapist. *sigh*