[Vent] My dog's in a frustrating situation and I'm too far away to fix it

Just need to get this off my chest because complaining to my boyfriend about it was not enough. So, I needed to leave the country for a month for work, and decided it would be easier and my elderly toy poodle to leave her with my parents than try to bring her with me to Europe. They have another dog who isn't super keen on adding a second dog to the household but they've always coexisted successfully, and my dog loves my parents and I generally trust them to take care of her various health maintenance (she has cushing's and just a fraught health history in general).

But while I'm gone, my older sister came home for an extended visit -- and brought a 10 week old dachshund puppy with her. Now, my older sister is actually a professional dog trainer, and my mother assured me that my sister was very adept at introducing dogs, and planned to keep them separated 'for many days' as a part of the introduction process (which I assumed referred to the two week shut down or at least something like it).

But now, less than a week later I asked how my dog has been doing and my mother says the puppy apparently has free run of the house and is using it to pester and harass my dog constantly. Moreover, my parent's lab (also elderly) is incredibly stressed by the third dog -- my parents now have her on Valium to help, but the lab is taking out her stress on my dog by snapping at her and stealing her food.

My sister, an ostensible professional, is apparently doing nothing to stop any of this, and is even compounding it by getting in repeated shouting fights with my parents and little sister who still lives at home -- I'm actually grateful my dog is deaf so that the fights don't stress her out as much because she's always been really sensitive to people yelling. But it's clearly also an element that's stressing out the lab, too.

Meanwhile, I'm thousands of miles away and can't get home for another two weeks, and I'm just really frustrated that I thought I was leaving my dog in a quiet, familiar home and instead accidentally subjected her to a super stressful situation all around, and I can't see any way to help from afar :/