"I love her opinionatedness."

Translation: Tôi yêu sự cứng đầu của cô ấy.

[Richardbrown1989]

Although grammatically sound, it sounds unnatural. 'I love how opinionated she is' sounds more appropriate.

[Dinhty1977]

Tôi yêu sự bướng bỉnh của cô ấy

[GiaLang3]

Opinionatedness (n) : "Sự cứng đầu" ; sự cố chấp.

[Shea603077]

'opinionatedness'! I love it, I am going to try to work this word into my daily conversation!

[Sontung_ntv]

Stubborn is just fine

[PeterThomp104763]

Posting an opinion here seems pointless, but I do so for what it's worth. At this stage in the process, there are combination words in the choices but never included in the correct answer.
To assist learning, I think it'd be valuable for words like "sự cứng đầu" to be blocked... as in blocked as the single word it represents.