Advice about aggression

I have an 11-month old female Canaan mix. She is spayed.
She is trained to "sit" and "shake hands", and walks nicely on the leash with no pulling. I have been taking her to the dog park every day since she was 2 months old. She loves people and plays nicely with the other dogs.

Recently, though, she has started attacking some dogs (the same ones each time). She appears to go for "fearful" dogs. She doesn't bite them, but forces them down and is extremely aggressive (lots of snarling and barking).

Any suggestion of how to cope with this would be very appreciated.

in my opinion, you would be best to find a trainer/behaviourist who uses positive reward methods to come and help you with your problem. Good luck

Sounds like she's becoming a stroppy teenager, I'd stop taking her to the dog park to limit her opportunities to bully and step up her training so that when you tell her no or leave it she does so in an instant. You don't actually say what you do when she goes for another dog. If she goes for the same dogs every time train her to leave those dogs alone when you do reintroduce her to the dog park or you might find someone else will step in and stop her behaviour as it's clearly not acceptable to anyone.