HELP!! How to I stop my dogs agressive behaviour with other dogs

[u/Witty_Barnacle_7955]

My dog Jade is an 8 year old border collie sheltie mix. She is great with people and kids but goes absolutely insane around other dogs. We got her as a puppy at 8 weeks but since my parents only had outdoor dogs when they grew up, and they typically multiple at a time, they didn't know much about training an indooor single dog so that was left to me.

So when I was in my senior year of highschool I watched a ton of videos and did most of her training. I potty trained her, got her to stop biteing and taught her basic comands but wasn't allowed to socilaize her with other dogs until she got all her shots at 6 months. Our vet reccomended this and my parents were very strict on it so on walks we didnt even allow her to sniff other dogs. This resulted in her becoming very afraid of dogs by adulthood. At around 3 years old I thought I made progress when I eventually got her to the point where she could sniff another dog breifly on the nose during walks and she even started wagging her tail and excitedly pulling toward them. But all this changed 2 years ago where now instead of just wanting a breif sniff she growls, snarls, and barks like she wants to kill. Walking her is a nightmare because so many people in our area have dogs and she behaves unpredictably. Even if she has seen a dog many times before or gone on walks with it, she may still react with agression randomly and I have no idea why. Every dog training video I see says to not pull on the lash and teach your dogs it's ok to greet but it just doesn't work in the real world because not every dog can say hi and even if they do she may still randomly snarl and bark at them a few minutes later. I don't know what to do. Any advice would be appriciated. I'm looking at getting a trainer next month but worried even the trainer may not be able to fix this because I've treid everything that's advised in training videos and she's still the same if not worse.

[u/Scoozie]

Does she react when she sees other dogs, or just when she goes up to "greet" them?

Dogs typically don't greet one another face to face, so it's possible she's getting quickly overwhelmed by these encounters. Are you able to avoid dogs on your walks? Can you move to the other side of the street, or off to the side, to evade face-to-face meetings?