Sometimes people will say something negative about themselves because they’re hoping you will say something positive, instead. I used to do the same thing. Whenever I was feeling insecure about my looks or weight, I would say something negative about myself, because my husband would tell me it wasn’t true and would give me compliments that would boost my self-confidence. I don’t do that anymore, because it’s not a very healthy way to be confident in yourself, but it certainly was effective. Do you think maybe your girlfriend is just feeling insecure about herself? I would talk to her about that to see if maybe it’s something she’d like to work on in herself. You can also try to give her honest compliments on a regular basis. It’s hard for a girl (or guy!) to feel unattractive if her loved one is telling her twice a day that her shirt looks good on her, or he loves her laugh, or he thinks she’s pretty.
My dog howls whenever she hears Piano Man by Billy Joel. That’s the only song she’s ever reacted to, and she does it every time. Her ears perk up as soon as she hears the piano in the intro, and she starts howling when the harmonica starts. She doesn’t stop until the song ends. I have no idea why she does this, and when I told her vet about it, the vet just shrugged and said, “I’ve always liked Billy Joel, too.”