So she is ok with dogs and people when she meets them? It’s just when she’s on her lead? So she’s leash reactive, she’s frustrated she can’t get to them?
It’s hard work, but you can definitely improve things. It’s never to late, but she’s practised this behaviour for a while, so you might need to put some work in.
There is lots of advice for leash reactive dogs out there and videos and books. I would suggest you first have a few sessions with a good, positive, trainer who specialises in reactivity, to show you exactly what to do and then you can practice it on walks. Someone who will go out with you on a walk and show you what to do in the real world situations.
It is best to practice at a distance your dog can manage before they react and slowly get closer. If she walks nicely in her lead up to a point, don’t go past that point. Avoid all situations (the best you can) were she is going to be in a situation were she explodes. With reactivity, management is a huge part of the training. Not letting her do it in the first place. Do not let her drag you over to a dog so she can meet them. Cross the road. Leave the park. Get back in the car. Etc. You have to be really consistent and do your very best to not let her go off like this. You may have to change where you are taking her and at what time. You may have to accept that you may have do some form of management her whole life.
I could give you a lot of tips, as I’ve been through this, but I very much suggest you find a really good, positive, dog trainer that can help you in the real world. They will be able to access her in person and your environment and give advice best suited to you. Some trainers have a calm dog that they bring along and you can train at a distance your dog is comfortable.
Do what you have to do to help you and your dog and don’t worry about what anyone else is doing. I put a training vest on my dog and wore a treat bag, so that everyone would know what was doing and would (hopefully) keep their dogs away from me until I felt comfortable moving closer. Every day and dog I saw was a training experience. I stood outside of dog parks, I played with him while other dogs walked by (so his attention was on me, not them), whatever it took. My dog would scream in the street with excitement when he saw another dog. If the dog was playing fetch and he was on his lead, I nearly got my arm ripped off as he wanted to run over and join in. I went from that to being able to walk past other dogs and ignore them. It was HARD work though.
They do get a bit better with age. But it’s very common with the breed unfortunately.
I will link some good resources a little later when I have time.And I’m sure other people will too.
Best of luck. She’s a sweetheart. X