My boss posted a job listing for my position 3 days ago. 10 days ago I had an evaluation where I was given nothing but praise

I don't think it was posted on accident because its a completly different format, is much longer, and has more requirements than when I applied. The wage is higher than it was when I applied as well. I am the only person with my position. I asked her if I needed to be worried about my job and she said no but it sounded really not believable. I think she is going to wait until they can replace me to fire me. I don't even know what to do besides keep working and look for something else