
As MM says, perfectly normal behaviour.
I have a nearly 3 yr old male Briard and a now 6 month old female Briard. From day one she has victimised him :rolleyes: He too has a very laid back, placid temperement and will tolerate everything. She lunges at him, shows her teeth, bites him all around the head, legs, you name it, if it's available, she'll bite it, she bahaves like Satans filly :D She bit him so hard last week that his brow bone was bleeding :( even then, he didn't murmur a sound.
Basically, the more he takes, the more she gives. She didn't get away with it with my old alpha bitch, one look from the older one was enough!!
Pups will always push the boundries, it's how they learn. Yes it sounds aggresive, but very rarely something to worry about :)