Why does my 7 month old puppy insist on this annoying fearful phobia behavior of new floor? What to do?

Personally? I'd feed her there, put her toys there... make it HAPPY SPACE! Play with your other dog on it, feed the dogs on it, and generally make it a place where good things are. Don't baby her, but also keep your voice happy and cheerful. It's a good place full of good things. It might remind her of where she was abused or something like it. Just keep things positive and don't push it.