Why did my manager tell me that my new job might not work out?

I’m I left a toxic job recently due to my boss being insufferable and controlling. She was making my life hell at work and it started to impact my mental health. She constantly made threats to fire me and I pretty much got the impression she wanted to eliminate me from the workplace. Then, I got a new job offer so I handed in my notice. As soon as she found out I got the new job she acted even funnier with me. She wanted to have all these calls with me and started using any opportunity to train me on new processes in the job even though I was leaving. She just wanted to have calls to tell me what to do and to show me that I was wrong. It was getting really intense. And then she asked me about my new job and when I told her about it she was acting visibly uncomfortable and her body language was very negative and she was grinding her jaw. She told me that I shouldn’t worry if my new job doesn’t work out because I can always find another job elsewhere

What was her problem? Why couldn’t she just be happy that I’d found a new job and got away from the workplace like she wanted me to?

Why did my manager tell me that my new job might not work out?
Post Opinion