Emze, I hope nothing untoward happens to this girl or this thread could put you right in the frame!
That’s the way to do it, wait unitl the person you’ve got the hump with has a very public dust up with someone else, then follow them home that night and bludgeon them to death. Other person is now in the frame……
(I’m assuming as you don’t mind murdering someone you don’t mind framing someone else).
Other option is to privately invite them round for a drink to discuss the problem, they’ll look confused when they find your front room lined with plastic sheeting. You can really get stuck in then, let all the resentment and anger come to the surface, I’d recommnend a claw hammer for weapon of choice. Helps if you have a tin bath, you can disolve the remnants in the bath then, can’t remember the chemical you can use, I’ll check the shed, might have some left over…..