"Her mother and her father"
Translation:Ihre Mutter und ihr Vater
The German reuse of words in different parts of speech is really difficult for me. "Ihr" can be second-person plural pronoun, third-person feminine possesive, formal second-person possessive, or third-person feminine dative. Same sort if thing for "ein" and "sie". I hope Duo is basing this on actual usage, not on abstract educational goals.