One
As discussed, this one needs background
Two
Amy Tan speaks lovingly and with great understanding about her mother's English and how they (mother and daughter) communicate differently when alone, and Amy Tan would say when she is with others who speak formally.
I don't know if you have what Tan said next. It is a great pity if you don't. It is one of the most beautifully written praises that a child can give to a parent: it is the recognition of the child that no matter how broken her mother's English, she knew things that were far more important than grammar and syntax. I'm sorry I digress.
The answer you want is three, backed up by 4, but the real answer is the aqua colored sentence. Tan is admitting that though her mother was in the room, she (Amy) was using stilted formal language which she realized her mother would never understand, and for herself it sounded phony. She wanted, it is implied, to be speaking in language that her mother could understand.