Is any of the ML paid? If it's all unpaid, then I can't see how they could force you to take your paid leave. If there is a paid ML entitlement, then I can see where that would come into it.

An extra few weeks of pay isn't all bad, but I'm hoping they aren't pulling a shonky here. All women are entitled to 12 months unpaid and I can't see that they can force you to take your paid leave before giving you access to the 12 mths. that's the case if you want to keep your leave. Let us know how you go. And that short notice is very unprofessional. Ask them to forward you in writing the policy that states you need to take the paid leave so that you can pass that on. I'd also ask to speak to the boss of the person who told you, they might just be confused or could at least explain it better for you.