The only time, it should overwrite the original, is when you edit the original and it saves with the same file extension. This can not happen with raw files, but can with tiff, png or jpg files. You can edit a copy or save as and choose another format. When you choose another format, for example a raw file then save as a tiff, you will see two files setting side each other, unless the option to not view duplicates is enabled. (In other words an option to hide other formats of the same image)
When you save over a file with the same name and file extension, no file gets deleted. It just over writes it.
You can either edit a copy, make a virtual copy and edit that, or save as a different file name or format.
If needed, I can go into more detail but I need photoshop and lightroom up and running to verify, so if anything is not quite accurate, its my memory playing me again.