Of course, I'm not a specialist.
Though, I do have anxiety and being pregnant ALWAYS makes mine worse. Your sister should focus on what she can control and sometimes that helps. Even minute by minute. For instance, I can control how much water Iím drinking, I can control the food Iím eating etc. Little sleep also makes my anxiety MUCH higher! Then she should go for a walk or something to get fresh air and her blood flowing while telling yourself positive things. It doesn't always work but itís worth a try! Today, she's pregnant and that's what important!