、。
Her car was so wonderful that her friends envied her.
Literal
She [topic-は] very wonderful car [object-を] was-having [because-ので], friends [topic-は] she [object-を] envied.
うらやむ ('to envy') has a related adjective 羨ましい ('enviable'), but the verb form is more direct — describing actual feelings rather than just calling something envy-worthy. 持っていた is the past of 持っている, where the ~ている form covers ongoing possession; the moment of acquisition is irrelevant, only the state of having. すてき is a casual, female-coded word for 'wonderful, lovely' often heard from women's-speech registers.