Hi. I'm a non-native English speaker.
This is a part of a play, Black Comedy written by Peter Shaffer.
CAROL: What about the girl in the photo?
BRINDSLEY: She lasted about three months.
CAROL: When?
BRINDSLEY: Two years ago.
CAROL: What was her name?
BRINDSLEY: Clea.
CAROL: What was she like?
BRINDSLEY: She was a painter. Very honest. Very clever. And just about as cosy as a steel razor-blade.
CAROL: When was the last time you saw her?
BRINDSLEY [evasively]: I told you . . . two years ago.
....................
I can't understand the meaning of this phrase 'as cosy as a steel razor-blade.' Does the word 'cosy' in this context mean she feels comfortable as if she were a steel razor-blade herself?
I would appreciate it if you give me a detailed explanation.
Thank you.