Not bat an eyelid

Not bat an eyelid - to show no sign or surprise or worry when something unexpected happens.

Example - "She told him she'd spent all her savings but he didn't bat an eyelid"

Image - http://www.quotehd.com/imagequotes/authors7/roger-clemens-roger-clemens-i-dont-bat-an-eye-at-stuff-like-that-ive.jpg