It's okay to be freaked out. I never find myself bouncing off the walls or anything when a potential metamour is mentioned but I do make it a point to see them all as individuals. This doesn't mean I don't consider the possibilities of things going wrong or the discovery of a cowgirl; it just means I don't use it against them especially since I don't actually know them.
You have to be cautious of your own projections. You have seen it happen with others and that informs your worry, but let her actions prove who she is instead of immediately writing her off from jump.