This is HyunA from a Korean pop group 4Minute. She also appeared on PSY's Gangnam Style music video.
I must say, it didn't turn out like I wanted, and it doesn't look like her, so I apologize. But if you're interested in knowing how she looks like, here's the link about her on Wikipedia.
Moleskine Sketchbook (5.5 x 3.5")
Thanks and Happy Mother's Day!