This is so incredibly petty to involve a landlord. First and foremost, these are personal disputes and not worth your landlord's time. She is a legal tenant and is on the lease; work it out amongst yourselves like adults.

And to play devil's advocate, y'all aren't perfect either.

First: your other roommate had no right to lock her dog in their room. I would have tried to "break in" to get my dog, too. Why the hell did the roommate lock her dog in there anyway?!

Second, removing someone's wet clothes from the washing machine and setting them on the dryer is just plain rude. What she was doing with her time was irrelevant - your other roommate was rude and wrong. Was what she did any better? No. But frankly I would have done the same.

Third: I had a roommate with a terribly trained dog. He would bolt whenever you opened the door, he frequently got into the garbage can ( he broke into the garbage three times one day while I was trying to take a shower), and was just generally a pain in the ass to deal with. The roommate refused to crate him when he wasn't there to supervise him and frankly, as I told him, it's not my job to watch your dog. So when he would leave for extended periods of time, I'd lock his dog in his room. The dog had chewed through easily $500 worth of my and my other roommates things that he refused to replace and I was sick of it. I gave him a bowl of water and closed the door. Is what your roommate did wrong? No. A bowl of water would have been nice, but the dog isn't going to starve to death or die of dehydration in a couple of hours (side note: dogs shouldn't be free-fed anyway. I seriously doubt he was "dry heaving from hunger." Source: I've worked in the pet industry with dogs specifically for well over a decade).

Plain and simple: you guys just don't get along. Is it annoying? Absolutely. But I'm sure she has just as much to say about you. This is not your landlord's issue. Put your big girl panties on and sit down with her and try and reach a middle ground.