Hurley brings Richard back to camp, Sun doesn't like Richard's plan

Sun returns to camp and Jack examines. He believes she may have aphasia which affects the language center of the brain. Ilana then smiles when she see Richard and Hurley return to the camp.

Richard tells everyone to pack up because they need to go to Hydra island and destroy the Ajira plane so Locke can't leave the island. Sun fervently objects to the plan of destroying the plane since she wants to leave the island with Jin, but no one can understand he impassioned rant since it's in Korean. She angrily storms off.

So is the loss of the English language really being caused by aphasia, or is it possible, as some have theorized, that Sun may have partially slipped into a time where she didn't speak English (like the sideways timeline)?