You've received some great feedback on this post
One question I noticed that you continue to ask is what happens if you run into her?
I have to advise that therapy will probably help you tremendously in this area. There are techniques that a therapist can work with you on regarding traumatic responses, anxiety, fear, or even if you have a strong desire to try to reconnect or talk to your ex in that moment.
My ex has stalked me well over 20 years. In the first years, we were very young, high school, and the lies she told classmates were awful and I was threatened on a few occasions by male boyfriends of hers. They would tell me I was stalking her, following her, looking at her. All of these things were very untrue(actually, she was the one doing this) but at the time I had very little support and I was so young, afraid, naive... . I almost started to doubt if I was or was not stalking her only because I was ruminating about our past, missed her very much, and grieving and I felt so guilty for ruminating about our "good times" that my self-esteem went to pot and I became very depressed. I had very little insight into my own self, her, what a healthy or unhealthy relationship was. I had dissociated with many of my childhood friends, friends who questioned my behaviors, I was so ashamed and hurt--hurt that they'd even imply or question my behaviors when they had known me since childhood and given that I didn't even do these things. It was like a nightmare... . I didn't understand how people could not see what this girl was doing. I got through HS by making new friends, keeping to myself, and keeping busy.
Fast forward to recent years. Lots of anxiety even up to about a year ago about her being around me. Same fears that she'd make stuff up and call the police, or talk to adults I socialize with and spread lies... .
It finally just took me understanding that I was giving her control over me. And what I wanted the most was ME back. I didn't want to live in fear, with anxiety, or ruminating about the next run-in. It took me realizing that I can only control me. If she smears me to someone, I have no control of it. All I can be is me. If she were to call the police or someone were to threaten me like in the past, I'd say I'm perfectly okay. I don't stalk her, I don't follow her, and if someone threatened me, I'd report it, too. No more being a victim and giving up my precious thoughts and fears on what-if's. She still does crazy things and I still get a "freeze" or fright and flight response(sometimes I don't have any physical reaction) but I have ways of coping now that help me debrief and move forward.
Years ago, Tony C gave me great advice in regards to your same question. Picture a horse race. Horses wear those blinders so they can only see the finish line, can't see what the other horse beside him is doing. Put on those blinders when you go out. If you see her, you have those blinders on and accomplish the task you were set on doing. If you're at the library picking up a book and she is in there, you have on your blinders. No need to say hi, no need to look... . you're picking up your book and leaving. If you're in a bar with some friends and she is there, probably a good time to leave but keep those blinders on while you do. Practice wearing your blinders with strangers.
