Respectfully, I think a lot of this advice isnt really reasonable for someone who hates conflict interacting with an ex-cop. Cops are trained and spend their careers practicing how to manage a space. Whether she is aware or not of what she is doing, she has a lot of experience on her side.
She’s your neighbor. She’s a PITA and wants a free horse with zero effort. You opened the door with a mumbled “maybe at some point”. Trying to get a restraining order or chewing her out is going to end suuuuper poorly.
I’d fake an incident. Don’t go out of your way to engage and the next time you intersect with her casually mention “oh ya, he’s going through that tricky phase. He spun and kicked out the other day. Thankfully he missed my head but wow!! He will get through it but he’s a bit tricky right now”.
Just wash and repeat. She doesnt need to know that he’s great and it doesn’t matter if he’s great when she sees him. Plant a seed that he’s a green young unpredictable horse. If she has the audacity to bring it back up “i’m so sorry. he’s just so unpredictable. I could never let another person on him”. Pull a black beauty. Let her whine about how her kids are great riders. Just keep repeating he isn’t safe and you won’t let anyone else on him.
If you can move your gates or rearrange things so that you dont have to get within earshot of her, I would definitely do so.