How do you emotionally detach from a toxic person?
Minimize contact in their life so they are no longer the first person you go to or the first person you think about. This can look like removing them from social media, reaching out to them less, not depending on them for your romantic emotions, and reducing communications to platonic interactions only.
How do I stop thinking about a toxic person?
Avoid escalation by not lowering yourself to their level. When they try to provoke you, just remain calm and composed and do not respond to their toxic behaviour. Ultimately, it is all about protecting your peace of mind. Don't increase toxicity, instead reduce exposure.