Is there a way to put her in a more enclosed space, even if it means putting an open crate in her playpen, just so she feels more secure? Perhaps the playpen is too open for her?
Also, as far as the housebreaking goes, I'm not sure how long you have to leave her at a time, but have you considered crate training? Or using an x-pen w/ a potty pad so she has a defined potty area?
On a side note, she is absolutely adorable! We're on a waiting list for a future litter than won't be ready to come home until spring, so the wait is killing us. My son was wandering by when he saw Butters' picture and said he hoped our puppy looks exactly like yours!
