Triangle pattern is a I wish I was hidden better pattern. So yes it's a sign of stress. Some display it more than others in identical situations.
She is likely pregnant only because of the way most of these are raised or imported. Care is not taken to separate males and females in cages or they are wild caught and nature has taken it's course. There is no specific pattern or color in this species that clearly identifies if they are gravid or just going to pass unfertilized ova. Babies are the most common out come with those recently purchased.