How does Earendil speak Beorian?

[Galadriel55]

Originally Posted by Hui

Okay that's actually adorable. Having him learn from Balar-dwellers means keeping Elwing unaware that the language still even exists, until Earendil reveals his lessons to her, possibly when he names his boat. (Though a CT note says that -wing as Beorian might have been dropped later, so maybe not that.)

Maybe that's the new question: did Elwing know Beorian, and if so, then how.

If I remember correctly, both Earendil and Elwing were kids when their respective kingdoms fell and they were sped away to the Havens. Elwing lived in the same Havens aa Earendil, with the same presumed Mannish refugees. Why would she not also learn at least a bit about her mortal side of the family while living there? Earendil might have learned Beorian independently or after meeting Elwing, but Elwing did not learn because of Earendil - she should have been flocked by the remaining Beorians. Of course they might have been speaking Sindarin when addressing her, but she would have been at the very least aware of the existence of their language.

What am I missing? Why would she discover the language from Earendil, when she could easily (re)discover it directly?