The dialogue you cite actually comes after Myra sees Hans through her window and after she already talked a little bit with Charlie about Mrs Kieslowski. She was quite sure she could drag the whole situation out a bit, just playing her roommate and waiting what happens. But once she saw Hans walking to the hospital to visit her, she became increasingly nervous, knowing that Charlie was looking for him and the time ran short.

And nervous as she got, she suddenly brought the conversation to Mr. Kieslowski herself, which is where your quoted dialogue starts. And I think this is exactly the point where Charlie at least starts to get suspicious about her. I think this can be perceived in his behaviour, since after she said that, he suddenly starts to stop his little playing around with the wheelchair he sits in and turns around to look straight at her, getting nearer and nearer to her. And at this point he starts to interrogate her a bit more about Mr Kieslowski and his visiting times. Maybe he already guessed it at this point or he just had a suspicion. But it surely didn't help Myra that she got increasingly nervous and started beating around the bush with stuff like "Different times, you know, not every day" (after previously saying a pretty definite "Every day").

So to sum up, I would say at the point Myra brought the conversation to Mr Kieslowki (so at the start of your quoted dialogue section) Charlie definitely got suspicous about her and his supicion was manifested by her nervous behaviour during the further conversation. Maybe he even wasn't 100% sure before his "n--ger" comment. But he was at least sufficiently sure enough and Myra certainly didn't deny it.

How does Charlie deduce Myra is Mrs Kieslowski?
I bought a new Lexmark Z1300 printer, I couldn't find any drivers for linux for this series, Is there any way to install drivers and make use of this printer on ubuntu 13.10 or i have to switch back to windows to take the printouts?
