Probably she has just relaxed enough in your home for her personality to start opening up. She sounds like she is just curious, and can definitely learn that the kitty is off limits. For now, I would keep them separated when you are not home, just a precaution, and keep on with the treats like you have been doing. I had a “cat workable” hound who was always very aware of the cats, but learned that the cats indoor were untouchables Outside is a totally different matter. I would never let the cat outside with the dog.