"She wants her letter to be starred."
Translation:Dia ingin surat dia dibintangi.
On the counterpart sentence forum (IDN-ENG), a native speaker said:
"Relax guys, this sentence doesn't really make sense in Indonesian either."
I also double-checked the meaning of "membintangi". According to KBBI, this verb means "to star in (a film etc)", or "to be the best/a champion". -- Example: Dialah yang membintangi kejuaraan atletik junior Asia. (it was the guy who starred in the Asian junior athletics championships.)
The only interpretation I can make from the exercise sentence would be "she participates in a writing contest, and she wants to win".
Anyway, if I were a course contributor, I would replace "surat" (letter) with "robot" or "kucing" (cat) as a movie main role. The original sentence is not funny at all and just makes us difficult to memorize the new verb.
You can use "mau" as well. However, there are some differences.
Formal vs. Casual -- "Mau" is more frequently used in casual situations. Meanwhile "ingin" is sometimes translated as "would like to", not "want to". Source: Q/A on HiNative.
Degree of eagerness -- "Mau" bears a stronger wish than "ingin" does. If you offer something to eat to your honorable guests, you had better say "Anda mau makan apa?" instead of "Anda ingin makan apa?" Using "mau" in this context implies that you are pleasure to serve your guests. Source: An Indonesian native teacher's website (sorry it's written in my native language Japanese).
Hope this helps!