Help with Resource guarding.

Hello! I have a 24 week old standard Xoloitzcuintli. Im having a bit of an issue with her resource guarding- a major issue that I don’t want to continue as we have another puppy (I know, I know) and I do not want her snapping. The puppy is much smaller, a scottish terrier and I’m worried she’s going to hurt her.

The snapping isn’t awful (more so in the air or just very light nips- she does lunge) but when she has any chews / treats, regardless of the ‘value’ she will snap (Not bite) at the younger puppy if she gets too close. She snapped at me today when I pet her and she had a bone. Absolutely fine after, and let me take it away. I’m just wondering if this can still be curbed? We can’t feed the dogs in the same room, nor can we treat them in the same room without distracting Branwen. She’s 19kg already, and I really do worry that she’ll injure me or the little one.

I am looking into going to a professional trainer, but I want to do some work at home with it too. Any tips on how to help with this would be appreciated, thank you!