Help what should I do???

Okay I'm not really sure where to put this and the situation is complicated so excuse me if I miss things but, I have this friend of 3 years and she's an online friend, we face time and she's 11 years old, I'm 14 and almost fully developed in the chest area, I know that kids just starting puberty are curious and stuff but she'll just randomly flash her breasts?? Like we'll be talking and then she'll go all quiet and just lift up her shirt. She's even asked me that I lift up my shirt too, which I would never do. I get super uncomfortable but I don't know how to get her to stop!! I don't want to make it awkward though...