Accidentally Two Accounts for Same Person

I am playing the role of IT for my mom this weekend, despite my amature-level knowledge of computers and have discovered that she somehow has created two users on her computer, one of her first name and one of her first and last name. I discovered this when looking up a file and found that she has two documents folders. I would like to delete one of the accounts but am worried about the implications of doing so. Her documents folders appear to be identical except when she moves a file, it doesn't move from both. I'm confused as to how she has saved documents to both users. She is oblivious to the problem, but I think clearing it up would help her use her folders with much less confusion.

Does anyone have advice about how to do this? Thanks!