STEP-MAMA PROBLEMS!!! 😰

I love my step children with all my heart. Im trying my best to teach them what would help them in the future. My kids go to their real mother half the week and then me and their dad get them the rest of the week. Now I'm very big on chores, they are old enough to clean up and learn a little bit of responsibility. My step-daughter is 12 years and she constantly brags about having chores at their mother's house and if they don't do it they get punished. SHE kept going on about how she tries to clean there everyday now because it's turning into a good habit.

I am highly frustrated at her because she always was good doing her chores but now she is slacking a lot. She's acting like she doesn't know how to follow the rules in the house even sometimes when her father puts his foot down. I'm thinking maybe she's at the age were she's testing the waters. My thing is, why doesn't she act this way at her mother's house?? i been with her about 3 years now and shes never been disobedient towards me. She knows being with us she needs to do her part before earning anything but apparently it's the same at her mother's house, so why is she giving us (mostly me) a hard time? Any advice?! PLEASE I'M OUT OF OPTIONS!!😭😭😭