10 year old niece won't wipe well

(quick background: nieces got taken from my sister due to her drug use and my father has custody and I'm living with him atm. So I've been trying to handle this situation for him since I feel it needs a more feminine touch lol)

I have no idea what to do at this point. This is the hundredth time I've found poop streaks and pee streaks in her underwear (mainly poop). I've tried explaining the infections you can get from not wiping well, I've told her people will notice the smell and sadly make fun of her with how mean kids are. I've even told her nicely she smells from not wiping. She knows how, she's just not doing it. Now, another issue is I'm convinced she might be a high functioning autistic based on my last roommate, my friends daughter and what her teachers have said when I had my dad being it up to them. We don't have money to get her tested so I don't know for sure. If she is autistic would that affect this? Is there any way to get her to wipe better or is this one of those ride it out situations? I'm at a loss and would love any and all guidance!