It's so different to me! I think it's adorable. She just kinda turns up the corners of her mouth back at me.
To explain what I mean when I say it's "different" --
Max (lab/irish setter mix) gives big smiles when he's super happy. I remember the 2nd time I met him (he's my bf's dog) he met me at the end of the sidewalk, and he stood there with his teeth bared, shifting his weight back and forth. I froze, thinking "oh god, he doesn't remember me, what do I do, what do I do?!" Then bf came out and was like "aww look, he's happy to see you!" Here he was so excited he was doing a smiley happy dance! I've only seen it a few times since then, which melts my heart every time I think about it now -- knowing that he was that excited to see me!