Well I like my own poppet spell, when cord cutting doesn’t work: it works fine on other people than yourself. I prefer using my own energy where possible, I feel it helps make me stronger, faster.
You could work on the person using Goetic entities a couple of ways…
Valefar can stimulate disloyalty (get them to be distracted by someone else),
Amon can break the relationship and create chaos between them,
Botis can cause a glamour of disfigurement to ruin the physical attraction,
Vepar can make them sick…
It goes on and on. I highly recommend getting hold of a Goetia grimoire, (I took the above examples from my personal fave, Corwin Hargrove’s Goetia Pathworking) and leafing through it. It’ amazing what inspiration pops out at you when you do that. Things you wouldn’t have though to search on just come to you.