As long as temps are good, she's moving around (even if it's during soaking/handling), she's eating, and her belly isn't distended, I wouldn't worry too much. My little lesser does this on a regular basis. She will literally look like a stuffed sausage. Not just the butt but her entire body. She eats like a horse and just takes forever to poop. When she does, she looks deflated again. Generally with impaction, they'll stop eating and/or you'll notice other signs such as a hard lump. Have you tried gently palpating her belly to see what you can feel? That might tell you if/where there is a blockage and it might also stimulate a bowel movement.