My slut neighbour Liv. She thinks we are friends but degrade her

So I caught her sneaking over to my neighbour's house. But he is my fwb during the lockdown.. so this fucking slut thinks she can just fuck my fwb because we are "friends". Also he is 57 so a few times now when I call him to ask if I can come over he tells me to come over after a few hours instead of right away like usual. This slut is draining his energy, I'm going to tell my neighbout to degrade her so she doesnt come back.