"She has a girl."
Translation:Tá cailín aici.
Yes. However, it wouldn't means "she has a daughter". EID shows that "The Smith girls" translates as * iníonacha Mhic Gabhann which uses the word for "daughter", so her saying "she has a girl" in response to "does she have children" would be Tá iníon aici. My guess on why this is is because cailín* can also mean girlfriend.