four month old lab puppy chasing and nipping our twenty two month old toddler at least twenty times a day and the toddler is starting to actually fear her, every source online has a different answer and i need to hear from families who got through this exact window before one of us breaks

Hazel is our 4 month old yellow lab, 28lb at her last vet check, female, we picked her up from a reputable breeder at 9 weeks. our daughter Nora is 22 months, fully walking and running, into everything, and the dynamic between them is the entire problem of my life right now. when Hazel sees Nora moving across a room she goes into full chase mode, nipping at her sleeves, her pants, her diaper, and now also her ankles, and the bite pressure is increasing as Hazel gets older even though we have been doing bite inhibition work since week 10. yesterday Hazel actually broke skin on the back of Nora's hand and Nora cried for 20 minutes and now refuses to be in the same room as the puppy.

what we have already tried and what is not working. one, baby gates separating them, which works but means Nora is in a 200 sqft section of the house all day and Hazel is in a 200 sqft section of the house all day and neither of them is happy and our marriage is starting to feel the strain. two, "trade" exercises where we redirect Hazel to a chew toy when she goes for Nora, which works maybe 40% of the time and the other 60% Hazel is too aroused to disengage. three, mat training with Hazel where she gets rewarded for staying on a mat while Nora is in the room, which works for about 90 seconds before Hazel pops up and goes for Nora. four, tiring Hazel out with three 20-minute play sessions a day plus mental enrichment work, which helps for about an hour after each session and then we are back to zero. five, our vet recommended a positive reinforcement trainer who came to the house and watched the dynamic for 90 minutes and said this is normal puppy behavior, will resolve by 6 to 9 months, and we should keep doing what we are doing. that was three weeks ago and it has gotten worse not better.

the thing nobody is telling me clearly is what the actual timeline is and what is reasonable to expect. i had a lab as a kid and i remember none of this because i was 9 when she came home, my parents handled all of it, and my memories start at "the dog who slept on my bed." i am now 34 and finding out that puppy stage was apparently a horror show that my parents protected me from. my husband and i are both working full time, both already running on 5 hours of sleep, both starting to wonder if we made a mistake. we love Hazel. we love Nora. we cannot keep them apart for the next 5 months and we cannot let Hazel keep biting Nora and the trainer's "this will pass" answer is not enough scaffolding for me to ride this out.

what i actually want to hear from people who lived through this. one, for families with a young puppy and a toddler at roughly the same gap we have (1.5 years between them, where the toddler is mobile but not old enough to follow commands about staying still or being calm around the puppy), what did the timeline actually look like in your house, and at what week or month did the chase-and-nip dynamic actually start to ease. two, what specifically worked when the puppy was at peak chase intensity (3 to 6 months), beyond the standard "redirect, reward, repeat" advice that everyone gives. three, has anyone hired a board certified veterinary behaviorist for a puppy this young and was it worth the cost (i am seeing $400 to $600 quotes locally for an initial consult). four, for the families who got through this and ended up with a dog and kid who genuinely love each other, what did you wish someone had told you at the 4 month mark. five, honest answer i need to hear, am i overthinking this or is the trainer underthinking this. i want to be doing the right thing for both my dog and my child and i cannot tell anymore where the line is between "normal hard" and "we need different help."