Thank you everyone and appreciate the advice that you have given me so far (except the idea of keeping my mom in some other country)
Thank you everyone and appreciate the advice that you have given me so far (except the idea of keeping my mom in some other country)
I speak Spanish, Italian and can manage fairly well if necessary in French. However, if I was going to take a citizenship exam in any of those languages I would immerse myself for at least a month in Spanish and Italian, and six months at least in French. I can tourist muddle in Portuguese so I would immerse myself for at least a year in that one.
The key to learning languages is to get down the "book learning" part and then to immerse yourself for enough time for your brain to make all the connections between book learning and conversation. It sounds like OP's mom has the "book learning" part down pretty well, so she really just needs the immersion.
OP,
If your mother is unable to communicate in the US, she is better off where she can. She can always remain a LPR with no language requirements, but I expect she wishes to sponsor other individuals which means she needs to get really serious about learning English as a good American citizen candidate would do. Yes, it will be difficult to learn a new language as an older adult, but she is the one who wants the privileges of citizenship.