As others stated, she thinks she is dominant over your wife and children, this needs to change. The most important thing is consistency, you, your wife and your children must be consistent and send consistent messages.
She needs to earn everything she gets and learn that your wife and kids are in control. Before she gets a snack, a toy, a meal or attention she must earn it. A simple sit, stay, wait, down, whatever she learns she must perform before she gets anything.
When you go out the door she goes last, wife and kids go first. If there are rules, such as off the furniture or areas she is not allowed it must be consistently enforced. It is a process that can take several months but it works.
Also, you start and stop play time, you control every aspect of it. If she doesn't behave or play correctly stop it and ignore her for a short period of time. Teach her how to take a time out. teach her to go and lay down somewhere when you want her to, again enforce it when needed.
Everyone providing any advice here doesn't seem to have experienced this and are not steering you properly. I have the same issue with a 1yr old braque male that is not neutered. Best advice is speak to a pro that deals with aggression. What shes doing is called resource guarding and very common in adolescent dogs and luckily not the worst type of aggression but I know the pit you're feeling in you're stomach when it happens, especially when you have kids. If you go at her, you'll likely escalate it. Remember, dogs dont care whether they get good or bad attention from you and it's an animal, not a 3yr old child that you need to educate. You need to redirect her when she grabs stuff. Make her want to give you the toy and let her know shell get it back and not have to guard her possessions. That means exchanging what she has for something else, even a treat. If I were you though, i'd call a trainer with experience in this. Also, google resource guarding and see of it fits her behaviour. You'll need to.be committed to how they tell you to handle it but eventually the behavior will fade. So far, for us it's working and hes better and it's been only 2 weeks but takes some time and careful management. Good luck! P.s. you dont need to kill the dog.