Is there a reason she is in a doghouse?

There's always a reason.

she has too many clothes on to be a human pet, but i can't imagine any other reason for her to be in there.

Not really "what", it's just a girl in a doghouse.

More like "why" instead of "what", yeah.

This is a fairly weird image, but it's in the realm of possibilities. Removing "what" tag.

She's a dog/wolf girl in the anime/game.

not really...not sure about the game. but in the anime she is just a highly skilled/trained maid/bodyguard who is basically a "watch dog". Shes loyal, playful, and protective. basicaly the dispostion of a dog. Does act like a dog tho when she has to "fetch" her food(beef jerky)