I'm going to ghost a former co-worker
Why would you ghost a former coworker?
We don't work together anymore, and I really don't think I want to talk to her. She's kind of boring.
That's fine, you aren't expected to stay in touch with old coworkers if you don't want to. However, it's good to end relationships on a positive note, instead of ghosting.
You're right, but I have nothing to lose by ghosting Jo.
If the relationship is more draining than productive with your 
 former co-worker, letting it go will be beneficial to you. It's good to make choices that help you grow, even if that means letting a connection go. I would end the relationship in a kinder way, though.