She can plan to start her maternity leave at any date she choses, but if she gives birth before her planned start date, it will automatically trigger her maternity leave from the day after the birth. So there's a really good chance (given most people give birth within the two weeks either side of their due date) that she'll actually end up starting earlier than her planned date.

In reply to Jacqueline:

Personally I'd try and talk her out of planning to start after her due date. ;-)

In reply to Jacqueline:

Hi thanks for both of your comments and good advice. I was going to recommend her line manager to speak to her just wanted to make sure I wasn't missing anything first - thanks very much - ps really like your pragmatic advice on other posts too.