Well socialized doggo turns reactive, any advice?

Hello guys!

I have a German shepherd mix, she's 14 months old, a girl. I've had her since two months old. She's incredibly smart and active. She's from a shelter – her, her siblings and her doggy mom were kicked out by the previous owner. They were found in the middle of forest on an illegal dump site.

We go on hours long walks, train – no problem. But as soon as she spots other a dog, she starts pulling, barking etc. She's not aggressive, she's anxious and excited at the same time.

We've started socializing her since she was two months old. She had no problems until she turned ~6-7 months old. We started working on reactivity immediately, but nothing works. She loves balls and treats but, if a dog is nearby… Nothing matters. She's perfectly healthy and she never had a bad experience with other dogs. We tried multiple methods but nothing works long time. I have two more doggies and they have no issues on walks or with other dogs.