Tips for agression towards other dogs?

Hi

I have a pair of wonderful spoodles (cocker spaniel, poodle cross). Our female is quite agressive towards other dogs she meets on our walks. She has been fixed. It seems to be especially towards larger friendly dogs that just want to have a sniff and say hello. Her brother is the opposite and is fine until she started barking, then they kind of "gang up" on the other dog. Very embarrassing for me their owner!

Any tips out there?

Thanks

Have you tried separating them and seeing how they behave alone? I have a German Shepherd who is fear-aggressive and a LabX who is friendly as can be--the GS used to bite first and think second with both people and other dogs when he was younger, but now he's calmed down. If I walk him alone he doesn't react to other dogs we walk past, but if the LabX is with him, she purposely gets him going by growling and immediately running over to the GS and nipping him so he starts growling and barking and tugging on the leash, too.

How old are they? If the female isn't too old, you could try socializing her; there are classes and animal behaviorists who can help with that.