Used most commonly by youtube star Natalie Tran on her channel, Community Channel. I is used when taking a compliment that was meant for you to compliment the person back. An end to the oh-so annoying back and forth of fake compliment giving girls usually tend to have.
Girl 1 : " Oh you look so pretty today!" *expecting to receive comment on how she looks pretty too*
Girl 2: " Baby, I know."