My 1 1/2 year old 45lb border collie is scared of strangers. If a stranger is around she gets low to the ground, extends her claws and growls. She has also nipped at strangers before. She is fine with non strangers though. She is lovable, and I can do whatever I want to her (including having her off leash) when there is no strangers around. I really need help with her. I would love to take her out in public but I can't because she is so nervous around strangers. How do I fix this problem? Thanks for all and any input.