That's so cute! My sister often comes with her friends and takes my pony collection and plays with them too. She gives the ponies names like "princess sparkle kite" (skyflier) or "beauty" ( a 25 anniversary cherrilie) or her best ever name, "river song" I told her it was a silver song, but I guess she misheard, and now we have a pony named river song.
Maybe she is secretly a Doctor Who fan.
Possibly, I mean, almost everyone in my family is a whovian, so she probably heard it from there.