I am 20 years old. I started out with a 190D 2.5 when I was 16 that my father gave me. It was a good car, 3 accidents, no scratches, on my body that is, lol, I cant say the same for the car.
I liked the 190, but now that I am older I just dont see the point in owning a 190. I have a 86 190D 2.5, 84 300D turbo, and a 92 300D 2.5 Turbo. I think next I am moving up to a S600 this summer or next yr. 190's are just too small, you cant really sit 4 people comfortably, nor can you carry a lot of stuff in it.
If you spend a little more money and get a 300D, defintly a turbo, she will be more happy. You see, you dont want to get a 84 300 diesels, they are very slow and very hard to drive for a teenager, mine often sits in the garage.
Also, because of its lack of takeoff speed, etc. its actually somewhat dangerous when pulling into traffic. Sometimes you need a car that has the horsepower to get up and go.
I think she will be happy in a 90-93 300D turbo. And gasoline engine is fine, but not as good gas milage. Another benefit of a later model is they have airbags, antilock brakes, etc. Goodluck and feel free to contact me if you need more info.