Help!!

My partners daughter is 11, I have an 8 month old too and I’m only 21, my issue is that his daughter is not wiping herself? She just can’t be bothered, she doesn’t flush the loo which is how I know she’s not wiping and I’m constantly having to wipe her pee off the toilet seat, she’s also extremely dirty and messy, we have to get her to tidy her room every day and it still ends up disgusting within an hour, I’m at my wits end, we’ve tried talking to her constantly but she just doesn’t seem bothered at all, any advice? It’s causing a lot of arguments :(