If she does it when you take her outside yourself, then it wouldn't be separation anxiety from you. However, if someone else takes her out or there is someone else in the house she is very close to, then it might be related to leaving them. Then again, she might just be scared to leave the home and is vocalizing her displeasure in the hopes you will stop making her leave. If you have stopped a walk short or are not taking her out as often and she doesn't want to go out, she has achieved her purpose by carrying on.
So lets address the possibility that this is separation anxiety. The first thing that I would suggest be done is to get a DAP collar. Dap collars use pheromones similar to the ones that a nursing mom uses to calm her pups. These DAP collars have proven effective for separation anxiety as well as other types of anxiety. That will help calm her a bid before you start training.
If she hasn't had obedience training then you will need to start that. The following site is helpful for teaching you how to train your dog. Be sure and click on the link to the page on obedience at the bottom. and links on subsequent pages leading to detailed instructions.
Training works best if you train at least 30 minutes a day (two 15 minute sessions). If she has had training, then start daily practice again to establish/reestablish yourself as the boss. I would start making your dog work via the Nothing in life is free program (NILF). It is outlined below.
You also what to teach her the speak and quiet command. . It seems easier to teach the quiet command after the dog has learned the speak command. The following site explains teaching speak and quiet commands.
You could use the quiet command to work with her on the separation anxiety. Of course if she is leaving you, the other person talking her out has to work with her. You can start by just putting the leash on her and let her trail it around the house until the leash isn't associated with going outside. Then start rewarding her for not making the noise when you put the leash on. Treat with hot dog (vienna sausage) slices or liver slivers. Dogs love these and they work great for training.
Once she seems eager to have the leash put on and you have been working on the quiet command, take her out the door and come immediately back in. If she doesn't make the noise reward her fore the good behavior. If she makes the noise, give a short tug to get her attention and a firm low toned NO before coming back in. It shouldn't take long before you can walk out and back in without the noise.
Gradually extend the time or amount of steps away from the house in order to get the treat. Once you are taking steps away from the house, give the treat before going back in. Don't try to move to fast or she'll start the noise again.
Now you have another option which would be go get a treadmill and let her walk on the treadmill instead of outside. Here is a great site on treadmill use for dogs.
Now her reluctance to be outside might be fear related in some way. In this case, the training I suggested should work for this as well since it will help her see that there isn't anything to fear from the outside and get her associating it with good things like treats.
Try these and see how it goes. I hope this information is helpful to you and you are satisfied with my response. If you would like any additional information or have more questions please don’t hesitate to press the reply to expert or continue conversation button so I can address any issues you still have .