Sorry for the double reply, but if i wait until masters first time is with melissa and then make deirlinn preg is that too late for her to give birth right before second freeze ?
No worries. To answer both:
It's still possible to get Trophy 21 if you have both optional Maids and complete their extra objectives. If you've also completed everyone else's and got the trophy for the first Freeze, that leaves you when an extra 'point' towards the trophy to replace the lost 'point' from Kala.
And yes. If memory serves, the game phase is 2 at that point, so Deirlinn wouldn't give birth until game phase 20, which I believe is the game phase the second Freeze ends on.