The details of this case really strike me on a personal level as I transition in and out of the German/English speaking world fairly often being a dual citizen. It is a shame that none of the items lend themselves in one was or another as to determining possible nationality (well, other than the remains of the passport of course and I suppose the German euro coins and cigarettes, though i see the latter items as incidentals acquired through travel). I tend to think, without any real justification, that this woman had more more familiarity with the English language/world. There just seems to be a prevailing anglocentrism about the objects. The language settings of the MP3 player as well as the music selection, The Calvin and Hobbes book in English, The Next clothing she was wearing (British clothing/dept store- I don't believe there are any in Germany).
As for why she has yet to be identified I suspect it is because she took extreme efforts to not only conceal her identity in death, but also to take her life in a place she and those close to her were unfamiliar and not likely to look for her.
I wonder if it might not be possible, given the good condition of her teeth, to do isotope analysis to determine her place of origin. I'm sure it is a last resort scenario but given what little there is to go on it might narrow the field.
For those who might have interest in looking the following sites have fairly comprehensive listings of those missing in the UK and Germany respectively since there seems to be some general consensus that these might be places to start. I have already browsed through and have noted two very remote possibilities.
(Germany, it is alphabetical under 'Vermisste Personen')
Also, Interpol's list of fugitive women;
I have also been looking at the following site to get insight into what the 'GET ACT.' logo on the sports bag might be for, it almost looks like a promotional bag to me the kind one would get for free from participation in or for signing up for something.
I really look forward to hearing any updates about this case.