Maybe she's a little overly cautious, as my second Yorkie, Jilly, always was. My Tibbe spent his first 9 mos. of life in a cage and you would think he'd be scared or aggressive toward other dogs but he just melts when he sees one. He's wiggly from his waist back, body bent in a kind of C-shape front-to-back, head kind of low, ears back, eyes squinted and respectfully avoiding direct eye contact, muzzle relaxed, soft, mouth open in dog laughter and play-bowing frequently to encourage other, nervous dogs to see it's okay to approach him. Still, if they hold back, he respects their energy and stops politicking and acts more dignified, still giving little invitations if they will be accepted but finally gives up and acts disinterested if it's a no-go. If a dog will join him and play, they are off and running in play.
The only thing I could suggest is just keep socializing her as much as possible so that she's totally desensitized to all kinds of dogs, always being careful to keep her safe if she acts unsure of another dog's hostile or dominant attitude.
Keep the sessions short and sweet until she acts happy around most dogs (unless she gets surly warning signals) so that each socialization ends, if possible, positively and she doesn't feel locked into staying near to a dog she might feel uncomfortable around for long periods of time.
I don't know if she's leashed during these sessions but often leashed dogs realize they are essentially bait and cannot escape at the end of that leash if another dog chooses to attack them so often they are tense when meeting other dogs while leashed unless you let them know you are in charge and relaxed, confident about keeping them safe in all situations or you get her out of there. She will "read" your attitude and relax more. So when you sense the other dog is friendly, try to keep a very loose leash so she senses she's got some latitude of movement if she needs to and a momma who is in charge of the scene so she doesn't have to worry so much about getting attacked when she's on the lead.
__________________ Jeanie and Tibbe One must do the best one can. You may get some marks for a very imperfect answer: you will certainly get none for leaving the question alone. C. S. Lewis |