I don't know that you have to "do" anything? Just listen? Feeling like you are breathing through a straw sounds like it would be very uncomfortable. Your response that you were sorry she was suffering was fine! Take what she gives and ask questions if you like, while on the subject; she will be able to tell you if she welcomes the questions or would rather you didn't ask, etc. Just keep in mind it is her illness and your "need to know" is very secondary and about you, not what she may want or need?