I have soooooooooo much trouble with tail gaters, I think I am gonna get a diesel, I never thought that way. But I must say (though I don't speak from experience) w123 is from what I have heard a very reliable car. And also there is ONE 240D with over a million miles on it in this world, which shows that these cars are reliable. I found out about that when I ordered that high mileage badge.
It also depends on your daughter. My first car (age 17, 1996) was a 1991 300E AMG, it was a beautiful car and I never let the rpm go over 2500RPM in any gear. I kept it clean and waxed all the time and tire polished etc etc, and I was the one who would remind my dad about when the oil changes etc were due. That car spoiled me so much that I tried 7 different cars after that and came back to an MB (420SEL)