In most comic storylines, Jimmy Olsen isn't a guardian. He's more often involved in reporting and assisting Superman rather than having a guardian role.
I'm pretty sure it's not real. There's no concrete evidence or reliable source to confirm its authenticity. It could just be a story someone came up with for entertainment.
In a more light - hearted scenario, Emily could be a mischievous pet, like a cat or a dog that has run away, and the 'catching Emily' part is all about the family trying to bring their beloved pet back home.