Puppy seems aggressive to specific child

[8feet12paws2fins]

Hi all,
I’m desperate for help and advice. We have a 6 month old cockerpoo and she keeps being aggressive to our 7 year old. She said never like it with anyone else, unless she has a treat which sometimes she will growl if you touch her (I know this is resource guarding). However, she seems to have taken offence against our 7 year old ds! He’s so gentle with her and absolutely adores her but sometimes if he strokes her, she will go for him. Not in a playful way or a puppy learning it’s biting inhibition, she really snaps after him. He knows how to behave around dogs and doesn’t bother her when she’s eating or sleeping, he’s never noisy or rough so I honestly don’t know why she seems to single him out (she’s fine with our other ds and all other people in general it’s just ds2). Ds2 has quite good reaction so manages to move away quick enough at the minute but I’m absolutely terrified that she’s going to cause some real damage one day! My anxiety is suffering with it, I’m so upset and I just don’t know what to do. Please help.

We experienced the same when we got a cockerpoo puppy. She was lovely with DH, DS2 and I, but would just 'go for' DS1, biting him whenever he was around. DS1 never provoked the puppy, but being biten by the puppy whenever he was around caused him a lot of distress, understandably. It was a very stressful situation and we ultimately made the decision to have the puppy rehomed.

We had a behaviourist for our havanese puppy, she advised us to keep puppy on a lead in the house so he was controlled all the time, we then had DD 4 at the time, give him commands he knew, sit, paw etc.. and she gave him a treat every time and lots of praise, we also used this approach when feeding him so she was giving him his dinner. This built up a positive association between pup and DD. 5 mins at a time 5/10 times a day. Within a couple of days the negative association he had with DD was gone, we reduced the treats and not had a problem since. This also worked well with resource guarding as she took food from his bowl whilst he was on lead and couldn't get to her, and directly gave it to him. A week or so and no more growling when she walked past him at dinner time. But all done on a lead so no chance of DD ever getting bitten.