Why is my neutered cat going into heat?

I adopted a neutered kitten, and now that she’s grown she spends her days and nights howling, whilst trapped in a halo of glowy love hearts. Mostly, it’s extremely annoying since there is nothing I can think of to stop her, but its also making me feel terrible that I have a seemingly always lonely and crying animal. It’s not only this one cat either, all of the animals I adopt are neutered, and all still go into heat and annoy the heck out of me. Is this a bug? Am I missing something? Suggestions to stop it?

P.s - I have unlocked all the doors so shes free to roam the outdoors, I’m lowkey hoping she goes missing so that I can catch a break from the meowing