Its up to you to do what you want! Spiritual Satanism is all about freedom and you have freedom to curse them or leave them be and move on with yourself.
If u want to curse them to oblivion then u can do it yourself or ask the gods to help you(in return for rtrs and such ofc)
Or if you dont feel like wasting any more energy on that cheating bitch then leave her be and rest easy knowing she will always be below you and will grow more and more depressed and unhealthy the more promiscuous she is.
something I've done on ungrateful partners before is do a love spell on them while we're broken up and refuse to get back together, make them obsessed and depressed without me(has worked!). Well warranted too, id never do it to someone who hasnt insulted/used me/cheated