You can translate it pefectly both male and female - so Miy druh should be also accepted.
There is a mistake in the correct solution for the male form: "Мй друг - продавець." I typed "мій друг" and got an error.
I've got the same! Shame on Duo!
When this sentence came second time I typed "мй"
and got it "correct". But it is still wrong. "МІЙ" is right.
Assistant isn't even necessary here. This literally is a "seller".
Shouldn't the female form of продавець be продавчиня ? Or is it not so used nowadays?