Agressive behavior normal? Behaviour

Hi everyone!

We have a 5 month old German Shorthaired Pointer & Blue Heeler mix. She's been with us for about three and a half months now. She's usually super well behaved in the house. She bites and nips playfully but we can always get that under control.

We have a big fenced in backyard so usually let her out a few times a day to do her business and play. The problem is whenever we go out there with her, she attacks us. It's different from the playful biting in the house. Her growling and barking is deeper and it seems like she's seriously trying to hurt us. It's gotten to the point where we all usually avoid going out there if we don't have to.

I know she's still a puppy (and she has yet to be spayed) but is this normal behavior or should we be concerned?

Thanks!

She might think the garden is her territory and she is guarding it. Not sure though. I would check with a trainer.

Are you sure it’s not just over excitement, some dogs are really noisy and seem rough when playing.

What happens if you have her on a leash and go outside at the same time as her? Also what happens if you go outside and she is inside but can see you?