Anyone with a child who has a scary imaginary friend?

My little girl has an imaginary friend called Andrew (we don't know an Andrew)She is 3. Andrew lives in the mirror and between the walls.He has 3 legs and when he is scowling at her she turns the mirror around to "keep him in " her words>She seems unfazed but my husband and I find it spooky.Where do they get t from.She only watchs pre scholl on TV and doesn't stay anywhere without us so not sure how this one came up!