Desexing border collie

Hey guys, my border collie is 4 months and just got desexed. I have read through many vet articles that suggest the 6 months desex rules, howvever, my veterinary kept suggesting to get her desex as soon as possible. My vet actually made this suggestion when she just turned 3 months but I was really unsure then. Afterward I received multiple emails from them telling me to come in a desex her.

I’m not sure if I had made the correct decision. I usually trust my vet but during the procedure they said she has something called a heart murmur and that I should have waited until she was 6 months for the surgery. I’m really scared that I fell into the vet pressure of giving her the surgery too early and this might hinder her growth. What do you think?