http://www.brd.nrw.de/gesundheit_soziales/landespruefungsamt/index.jsp
The Landesprüfungsämter (LPA) are responsible for transfer of medical school credits. If your fiance was born in Germany, she should ask the LPA of the BUndesland she was born in. As fars as I know, the LPA in Nordrhein-Westfalen (see link) is responsible for foreign-born student's accreditation. They should be able to tell her, what her German semester-equivalent would be (ie. if she'll have to repeat semesters or if she can transfer directly).
Then she'll have to apply to the university she wants to attend and provide them with all the necessary documents (along with what she gets from the LPA).
A heads-up:
Some medical schools don't take any students before the PJ (praktisches Jahr), ie the final (purely clinical) year. Others will require her to start at the beginning of the clinical part of training (ie. beginning of 3rd year).
So, I'd recommend contacting the LPA then researching medical school admission requirements for higher semesters and go from there.
Not sure how medical school in Romania works... if she has a 6-year degree with a final year of clinicals, it might be easiest to transfer at that timepoint.
I have no personal experience with the whole process, but the info might still help.
Good luck!