Yeah, Bom has a lot of extra weight/skin/something below her chin. I especially noticed it in Naega Jeil Jal Naga's MV. Her lips look overdone, too; they have a really weird, puffy look about them and they hardly move when she sings. @_@ That plus the fact that her face looks like it hasn't aged at all since she was 6... just make her really, really weird looking to my eyes.
I think she just has an unfortunate face shape that kind of naturally looks like those old ladies who have had a bajillion plastic surgeries, plus fake lips and make-up artists who have no idea what kind of make-up would flatter her face. Seriously, the eyeliner is way too much on her. It just makes her look more plastic. She is so cute in pictures where she doesn't have so much eyeliner on.
Anyways, yeah, she has a chubby/puffy face and lips.