I used to be so frustrated because I couldn’t get my magick to work on my boyfriend. And then, I realized that when I connected with his energy instead of just saying his name in ritual, it ALL started working. He has this ancestral protective entity that I’ve seen and spoken with and I think maybe she has to do with my not being able to work magick in the beginning.
In my view, it’s about learning how to work someone’s “energetic” systems. As I got to know him better and as I started connecting with his energy more, my magick related to him got stronger and stronger. I’ve never used it to “get him back” or in a manipulative way, but the target matters in magick and the more practiced you are (in general and specific to a person), the more results you’ll get.
Here’s the thing though, when you connect with someone who has their guard up against you, for example someone who broke up with you, you’re not just met with their energy signature. You’re met with whatever guards and walls and spirits they keep around them. Some of which are inclined to attack whatever touches them.
I’m with @Mulberry . You’re gonna have your shit handed to you.
…that doesn’t mean that you can use it against her and everything will be fine.
Demons don’t work the same for everyone who uses them. Will matters, protection matters, intention matters. While Sargatanas can probably bypass her defenses, that’s not the only thing that matters.
*I’m not sure how much experience you have, so I’m operating under the assumption that you don’t have much.