"My sister talks with my mother."
Translation:Min søster snakker med min mor.
Thanks, that clarifies the grammatical difference.
I was interested in if the "sin" version would be accepted since if she's my sister then by definition we have the same mother.
The ambiguity is also there in English with "My sister talks with her mother" vs "My sister talks with my mother"
I was surprised to learn that duolingo has a very basic mistranslation. Mother should be translated as "Moder". Danish has its formal and informal versions of this pronoun as well. Mom= Mor, and Mother= Moder. Likewise, there is Far, and Fader, for dad and father. Nt a big issue, but just FYI.