How do I choose a language class for my daughter when her conversation is ahead of her reading?

The placement teacher spoke Mandarin with my daughter for several minutes, then put a short reading passage in front of her. She recognised a few characters and guessed the rest.

She's ten and speaks Mandarin regularly with her grandmother. We enrolled her in a Saturday language school because she wants to write messages to Grandma as well as send voice recordings. The teacher suggests a lower reading group. My daughter says most children in that group are younger and that she will feel like a baby.

I had told her she would probably be in the advanced class because she speaks confidently. That was my assumption, not the school's promise. The higher group moves quickly through written work she can't yet do.

What should I ask about the two groups before deciding? I want to take her embarrassment seriously without placing her in lessons where she spends every Saturday pretending to read.