I rarely sign onto this site either any more but for different reasons.
However, in MOST cases getting your cat spayed does indeed stop the behaviour. If your cat is once more in heat then may I suggest another trip to the vet to figure out why? If she is only acting this way every six months I would hesitate to say she is "in heat". Cats in heat normally cycle every few weeks if relief, mating, is not achieved or spaying not done. Spaying, as stated by my long time friends, will end that. I don't believe they intended to make people feel stupid on purpose. Maybe their intent was interpreted wrongly? Spaying is a simple fix.
I too have a couple of girls who "act" as if they are in heat at certain times of the year. They aren't. They are just overly affectionate in the spring and again in the fall. Weather fluctuations seem to affect their behaviour at those times.