am i over reacting. !?

So me and my sis live together and she has four kids and only one of then which is the oldest lives with us . On my side i have a 6 yr old kid and a five month old and my bf stays here as well . So on the weekends my sister bring her kids over to spend the weekend . They dont bother me but the only thing that does bother me is that my sister doesn't discipline them . She just stays locked up in her room on her ass in her phone . Shes way older than me like by 11 years. Bullshit u not her kids , they always leave a mess !!!!! They always leave a mess on the table and leave their dirty as plate on the table and the dishes just pile up !!!! Or when they finish a gallon of juice or a box of cereal they just leave the empty box or gallon on the table. Also They can at least wash their own plate. Im the type that doesnt like cleaning uo after nobody ! I only clean uo after myself and my six year old daughter . And when they use the restroom they just throw the TP in the trash like it aint no thing and it falls out when theres alot of space in the trash bag still . They can at least press down the TP so it wont fall out and look nasty asf!!! Theyjust left , and left their fckn mess for me to clean up like always . And i had enough !!! They are not my kids for me to tell them what to do . Thats my sisters responsibility not mine. Am i over reacting or not ?!