"Grandmother is promoted to engineer by the queen" would be correct.
"Promoted to be" is unnecessary in English, "promoted to " is sufficient and the way that it is commonly said.
And "by queen" is incorrect. Adding the article ("the queen") is required.
That's fine, but "promoted to be" is still correct. For such a correct answer, Duolingo usually adds the message, "Another correct answer: [alternative.]"
"Grandmother is promoted to become an engineer by a queen" is also correct and a more literal translation of "menjadi". Seharusnya diterima juga.
"The/my/our Grandmother WILL BE promoted to engineer by THE queen" would be better, even so, I would think people graduate as engineer, they are not promoted.
I suppose there could be a title of engineer that one could be promoted to, but I would suggest even then the sentence in English should be "Grandmother will be (or was or is being) promoted to be AN engineer by THE queen.
The degree in engineering is normally conferred by a university. Not sure how a queen would "promote" someone to become an engineer.
I was not given the option to choose 'the', before queen, however I was corrected and marked down.
'the' needs to be added to the list of possible words.
I would think she is either being promoted or was promoted