IMO its best to separate the pregnant sow to her own quarters for farrowing about a week before her due date this gives her time to settle in and prepare her nest for the babies. She can still be within nose touch/sight of the other girly but not so other can pinch, roll on or kill the piglets either on purpose or accidentally.
See
www.gospbc.co.uk tab pig management for more info on farrowing.
The big girls can usually go back together either when the piglets are weaned or if you are 100% sure the other pig will not attack them when they're 3 or 4wks old(personally I wait until weaning) You will find Doreen will be very protective of her young and she might be aggressive with Delilah and see her as a threat to her young so be aware.
You can big fuss (even more than usual) of Delilah so she doesn't get too jealous of Doreen & the piglets. Best thing to do is play it by ear, you know your pigs best.
Good luck, exciting times ahead.
mandy