I'm pretty sure that "She hurt her head" is also correct. 了 indicating the past/change and all.
Along those lines, "She injured her head" should also be fine.
"Her head got injured" should also be accepted!
Have you pressed the report button? (I just did)
Because 7 months later, it still isn’t accepted.
The audio for 了 should be changed so it is the correct one, instead of the 了 as used in 了解，等
Because of the 了, shouldn't the answer say her head 'was' injured, not 'is' injured.
So you've met my ex wife!