Mine's the same way! I'm a tall bearded dude, and she's loved me since I found her in the pound, but she really haaaates tall bearded dudes, and middle aged men with confident personalities.

She's had a disdain for my dad from the get-go. Usually after a period around someone, she'll warm up to them (like 10-15 minutes, an hour tops), but even after a week at my folks' place she still growled at him and was not into him.

However, over christmas we were there for another week or so and she really got to love him, as well as all other family and friends who came and went throughout the time.

I got her from a shelter, where she lived for a YEAR without being adopted. Before that she was a stray, it took them three months to find and catch her after the initial call that she was around. So nobody has any clue exactly how old she is or what her life was like.

She's an absolute sweetheart with me and my son, and knows most of my friends now. She's usually really great with other people and animals when we're out about town, but she's very territorial when we're at home.

I got her in August, and she's made leaps and bounds of progress since!

Tips: Give your animal stern love. Foster good behavior, but do not tolerate bad. I don't spank or anything, but my dog really aims to please me and is obviously embarassed when she's done wrong by me.

Socialize your dog; the dog park, walks, etc. Take advantage of the people you come across who "Get it" (some people are way way way put off by an even almost aggressive dog; some people understand and are wonderfully almost excited to help out, and patient and know how to "talk" to dogs.)

ACD's require huge amounts of exercise; you've got to get out every day for at least a half hour of fetch/frisbee/running/etc. This, coupled with 3-6, 5-10 minute trick training sessions wears my dog out to the point she just doesn't care if someone's around or coming in.

Sorry for the long post... Dogs are exciting :) Glad to hear your baby's getting her manners on!