She should wait until she receives an offer to bring up the maternity issue. If the company believes it can do without her services for a specified period, her pregnancy won't matter. But if she's to play a role where her absence would create havoc, it's in her best interests to graciously allow the employer to withdraw the offer, asking if she can check back with the company after she's ready to return to work.
Although the Pregnancy Discrimination Act of 1978 made it illegal for employers to discriminate against pregnant women, a wise woman will take a long view of working relationships. An employer who feels ambushed may get even in subtle ways that make your friend's working days intolerable.
DEAR JOYCE: You once wrote about getting what you want by asking questions. Can you refresh my memory? - U.R.T.
Learn to use innocuous, but powerful, sales-oriented questions to persuade others to accept your point of view:
"Should we take another look at the design we shelved last year?" "Why do you say that?" "Can we come to some agreement on this issue?" "You know, this job sounds like it is something I would really like to do. Is there a fit here?" "Is it convenient if I check back with you periodically to stay current with your decision process?"
Entire books and online articles articulate the concept of "The Art of Asking Questions." Explore.