What does it mean when an older korean woman calls me lil bro?

So I've been hanging out with a Korean American woman (29) that is slightly older than me (just turned 29). She's very korean.

We usually hang out in small groups and we always sit next to each other. We are also the two left talking to each other at the end of the night or when the others go off walking around the club / bar. She's shy and slightly reserved and I'll make compliments and she will flirt with me once we both have some drinks (her head on my shoulder, spraying water on me, jokingly calling me out on random stuff, etc). However, she called me "lil bro" the other day (I'm slightly younger) and I'm not sure how to take it. I know in some Asian cultures they call each other brother / sister and some have different meanings (they like each other, they see each other just as close friends, etc). I was wondering how I should take this. I definitely have feelings for her.