Unique purchase advice – diesel for 4000€

Hello, was invited to my niece today. There her girlfriend approached me and said you know yourself a little bit about cars. She recently scrapped her car and is now looking for a new vehicle for 4000€ and it must be a diesel? Actually wanted to talk her out of the diesel. But she says her parents would pay the car tax, insurance and fuel (diesel) at a diesel truck. Should she buy a petroler you would have to pay for everything yourself. She only had to pay for the vehicle. Was then a bit perplexed. Which (diesel) car for 4000€ should be recommended to an 18-year-old girl? Km-driving performance she could not tell me either, because she only has the driver’s license for 7 months. We could then at least calculate the kilometers for the driving distance to work. There she comes to about 9000km. Which vehicle would you recommend?