A darker triangle behind the stomach is a good sign she is pregger. My Swordies get really fat and start to look like the pictured fish a week to ten days before they birth.
Here's a couple of my pregnant lyretail swordie. It's very difficult to see a gravid spot on her coloration but she should be having them any day now. I was going to try to take some of my Marigold Wag female who is also pregnant but she refused to come out and play. I suspect she is about to have babies right now as she is hiding.
Was going to try to take some more pictures of my pregnant girls but while I was doing a water change I found fry. Apparently my marigold wag female is no longer pregnant.