Learning to talk

C's talking has improved quite a bit. Still she does not say appa or amma properly or whenever we want her to. But she says them whenever she feels like it.
She also says really serious sentences of 5 to 6 words. Sometimes she says 2 such sentences continuously. During this elocution, her face is also very serious, as if she is saying something very important to us. Only thing is that we dont understand a single word. Typically we dont know whether to respond to her in 'her' language or in Tamil.
She says pappy (for paal for milk) and but yesterday when I offered milk to her when she said that she didnt want to drink.