My daughter makes messes

Hi everyone. I'm new here and looking for support and advice.

My 11yo daughter has autism and for the past several months has been making big, nasty messes everywhere. We can't leave her alone for even a few minutes. Here are some reasons why: 

She thinks it's funny to pee on the floor even though she has been potty trained for a few years. We never punish her, but always tell her, in no uncertain terms, to go in the potty. She just giggles and bounces off.

She often screams as loud and long as she can. We have no idea why. Food often helps, but not always.

I keep literally EVERYTHING locked up and she still gets into things. The other day I found iron filings from my son's science project all over the carpet in my bedroom. Not as bad as the pee, but still a mess.

We have turned our front and back door knobs around to keep her from running outside without us. This works well, but I fear she could still get outside without us knowing. It's scary.

And countless other inconveniences. Sometimes I feel like I'm at the end of my rope.

Any non-punitive suggestions welcome.

Thanks in advance.

Kate's mom