This is the 17749th most frequent Russian word.
украинку
"Украинку" means "a Ukrainian woman" in English.
Here, 'украинку' is the direct object in the sentence referring to a Ukrainian woman.
Я встретил украинку на конференции.
I met a Ukrainian woman at the conference.
In this sentence, 'украинку' is used in the instrumental case to describe origin or identity.
Пециалистка по языкам оказалась украинкой.
The language expert turned out to be a Ukrainian woman.
'Украинкой' is used here in the instrumental case to describe the person with whom the action takes place.