is my dog aggressive or fearful?

I think its fear, but sometimes the signs point to aggressive.
she always barks out the window at people passing, mainly its if they are walking a dog, or if they look like they are walking a dog. If people come to the house she freaks out barking, generally she stops when they enter the house and present themselves,after a few minutes of her pacing around. we do not have many people come to our house, but she does bark at people she knows . Some times the hair on her back is raised sometimes not. Its mainly its a quick "ruff.ruff.ruff.ruff" and nothing will get her attention. sometimes its a low growl b.c she knows im in the room and will tell her to stop. she just loves to sit in the living room on the couch and watch out the window and do this. The most logical thing would be to move the couch, but my husband insisted on buying this giant sectional and it literally takes up the entire living room and I cant move it.

so back to my question. I really think she is barking out fear of the unknown. although she has also started nipping at other dogs lately. she only nips at them if they come near her, other wise when we are out she could care less when she sees them.

The only reason I am asking b.c there was a episode of "its me or the dog" on tv(animal planet) that showed a dog (I think a american bull dog) that barked when people came over. the only difference (with my dog) was this dog would bite them if they came in.
I dont want it to get to that point.
So how can I approach this with our dog, since obviously everything we have been doing is not working.

Barking is a very self-reinforcing behavior - dogs do it because it's fun for them to do. She enjoys barking at people out the window, and the more she practices that behavior, the more she will probably begin enjoying barking at people in other places, as well. I don't think it will solve your problem completely, but I do think that you should teach her to stay off the couch, or teach her that barking out the window makes her loose her couch privalages (as soon as she makes a noise, get her off the couch and don't let her come back up until she's calmed down). Letting her continue practicing this behavior will probably only make the problem worse.

To answer your question, though, about whether this is fear or aggression - it's probably both.... fear-aggression. Most aggression is actually caused by fear - the dog is afraid of something so s/he acts aggressively to make it go away. You can tell that it's fear aggression by subtle differences in body language. The easiest way is to watch when your dog is barking - does she move backwards at all? Even if her body posture is leaning forward, many times she will hop or walk backwards as she barks, this is an indication that it's fear aggression.

thank you for getting back to me. I do understand her sitting on the couch and barking out the window is def. a problem. Do these things work http://www.jbpet.com/X-Mat,2112.html?src=Google28&gclid=CJPJ4ceh-pQCFRKhxgodawQTrQ ?
Im just fearfull she will bite someone. I have 3 kids, with that comes friends over the house once school starts. Can this behavior be worked out?
My husband thinks its also her age, he says shes in her "teenage years"That this too also will pass. we are re-doing basic training with her as we are working with our puppy...some days I feel like ive gotten into more than I can handle. She used to be a totally different dog before we got out pup.

I've never seen the x-mats before, I'm not sure if they work or not. What I would suggest is to make sure that you prevent your dog from getting on the couch if you're not in the room - you can use a baby gate or close doors to keep her out of the room, or I used to put chairs from my kitchen table on their side on the couch to block the couch, works fine if your dog is big enough to not be able to lay under the chairs - and when you are in the room, of course, prevent her from getting on the couch, or get her off when she does get up. You can also teach her to come up on the couch when you invite her, and if you didn't invite her she's NEVER allowed up on the couch.
It's really impossible to say without actually observing and seeing exactly what she's doing. I'd suggest getting a trainer who can come over and watch her reaction to strangers, to first figure out if it is true aggression or fear aggression, and then how to fix it from there.

Great advice from Lizzy.

I would also teach the dog an off command for when she does jump on the couch, and a place command so you have somewhere else to send her. You can use a dog bed or a mat - I used a bath mat for my dog - as a place.