I find that when females are nervous they lose their color much more quickly and they get stress stripes much easier than males. I had two females who were faded and constantly had stress stripes for the first few days that I had them, and then after those few days, they would get their color back once in a while, but if I made a quick move near the tank, they would freak out and get stress stripes again. It took a few weeks but they calmed down and stopped freaking out when I walked in the room. lol
When I put 6 girls in my 55 gallon community tank last week, two of them, who I've had the longest, got stress stripes and were faded out for a few days straight. I think it was the move, plus being with new bettas and other fish, and also I had a dwarf gourami that was harassing one of them (I brought the gourami back to the store because of it). But now it's been 4 days and they only fade and get stress stripes occasionally and they don't last long.