Girl Who Puked on Gaga -- Chill Out Demi Lovato ... We Didn't Glamorize ANYTHING!

The girl who puked all over Lady Gaga's chest during SXSW this week says Demi Lovato needs to calm down ... because their performance wasn't meant to glamorize squat.

Performance artist Millie Brown tells TMZ ... she and Gaga did not intend to offend anyone struggling with bulimia -- they were attempting to challenge the concept of beauty.

Millie says, "there's a clear difference between using my body to create something beautiful, to express myself and feel powerful, rather than using it to punish myself and conform to society's standards."

As we previously reported ... Demi blasted the performance yesterday saying it glamorized bulimia.