White button on home screen!

So my aunt ended up messing with her phone and now a white button (shutter button) is always on the screen at all times. (It is not the home button on the screen) it only opens up the camera app. I have looked in the camera settings, home screen settings and accessibility (not touch assistance either) and can't find it. Please help, she keeps hitting it and it open her camera then she gets very confused and annoyed! For the iPhone XR updated to 15.3.1! Thank you!!