Resource Guarding - Humans

[curleetop]

Here is the situation.
My partner and I took in an Australian Shepherd named Levy two weeks ago. She’s just turning one and she came from a young man who I’m fairly sure spent the last year ignoring Levy for the most part. When he wanted her to get out of the way he would boot her with his foot (that seems the extent of the attention he gave her)
All in all she’s an excellent dog. She learns quickly and super friendly and seems happy with us. She’s picked up “sit” and “lay down” with verbal and hand signals and she’s now getting “head down” as well. I’m starting her on clicker training too, as she’s both affection and food motivated.
She’s also been slowly introduced to our two cats (very slowly) and she’s actually doing fine with them at this point.

The issue that has come up with resource guarding but with a twist. She’s guarding anyone around her from other dogs (including the dog’s owner) If I am standing and a dog comes up to say hi to me, where ever Levy is, she’ll run over and stand in between us. If the dog goes then to her own owner for attention, Levy will sidle over and slide herself in between. She’s not unfriendly to the dogs at all outside of this situation, but at some point she snaps a warning at the other dog. We’ve been trying to pet both dogs at once or re-direct her attention but I’m not sure if we’re treating her/this situation correctly.

Any advice?