Our dog only has accidents inside when I’m not the only one home

A little while ago, my parents got Mochi, a Lhasa-Pom mix, and she’s about a year old. She wasn’t potty-trained when we got her, so we’re all trying to fix that, but our efforts are really uncoordinated. We’ve had her for a couple months, but she’s still not potty-trained.

Last weekend, I was alone and in charge of looking after her because my parents left to visit my grandparents and my step-brothers were going to their dad’s. I let Mochi out every two hours or so, and if she went to the bathroom, I would give her a treat and continue to let her play outside. If she didn’t go, I’d let her inside without giving her a treat. When I went to bed, I gated her in the kitchen (we don’t have a kennel) and set out a pad in case she had to go, and she never used it. I did this consistently all weekend, and she only had one accident. I was in the same scenario around the end of January, and it went pretty much the same way.

Everyone came back Sunday night, and left for school or work the next morning at 7 (I’m home most of the day and work/take classes at night). I woke up a couple hours later to let Mochi out, but she’d already pooped and peed on the pad. My dad lets her out before he leaves for work, so she had to have gone between seven and nine. I kept the same schedule of letting her out until around two, when my brothers got home from school. An hour later, she peed on the floor.

Is there any reason for this? Am I missing something important, or is it something to do with the rest of my family? I don’t really know about dog training other than what I’ve read online, so I’m probably doing something wrong.

And it’s kind of off-topic, but Mochi isn’t even my dog. She’s my parents’ dog. I’m planning on moving out this summer, so I don’t want to be the primary caretaker of Mochi, even though I sort of am already. Do you have any tips on how my family could better share responsibility? Maybe a schedule or something?