I don’t know how productive it will be to compare the two…
Completely different backgrounds (bourgeois foreigner versus old nobility from the same country), and not exactly the same time frame either, as the relationship of Silvia Sommerlath and (then) Crown Prince Carl Gustaf began in summer 1972 when Silvia was already 28, and Diana’s and Charles' started in late 1980 when Diana was only 19...
After growing up bi-lingual in Brazil and returning with her family to Germany in 1956, Silvia graduated High School in Heidelberg in 1963 and then moved away to the big city Munich. Originally wanting to become an elementary school teacher, she decided otherwise, went to an interpreter school and started working as a translator and interpreter.
In the late 1960s, she worked for the Argentinean consulate in Munich in that function, before she landed the job as trainer for hostesses for the Olympic Summer Games in 1972. She never was, as popular myth would have it, a mere Olympic hostess herself. Additionally though, she acted as one of the ‘faces’ for the upcoming Olympics, actually promoting the Games in PR films, in TV shows and photo shoots.
During the Summer Games, she met the then Crown Prince of Sweden, after two other long term relationships she had before, one with a lawyer, the other one with a businessman.
She had by then established good relations with the Vice President of the International Olympic Committee Willi Daume and became deputy chief of protocol for the Olympic Winter Games in Innsbruck/Austria, planning the schedules of events and guest lists protocol-wise in advance, and of course during the actual Games in early 1976.
Her engagement with the King was announced a little more than a month after she finished that job.
Her career path was actually ahead of the time back then for a woman of her conservative, bourgeois background. The usual expectation in early 60s Germany would have been to maybe start some studies and even begin work as a teacher, but be married with kids before reaching thirty and probably also to stay at home as wife and mother.
As I said, the biographies of Princess Diana and Queen Silvia are quite different.