apostrophe in user email

There is one user with an apostrophe in the email address, but wordpress will not allow that character: ERROR: The e-mail address isn’t correct. (which is a crappy error message, really)

This user doesn’t have any other address to use.

How can I get wordpress to accept the ‘ as part of an email address?

From the research I’ve done it does seem strange this is the first time she’s encountered an issue, but maybe there’s something simple I need to do to make the address “correct.”