She's simply not interested in you, OP. You shouldn't have bothered to ask her for Skype or Snapchat after - if she wanted you to have them, she would have suggested them on her own; now she thinks you're desperate, and possibly creepy.
You're not a bad guy or anything, and I'm going to assume you're about 18 due to your first sentence. Rather than trying to talk to chicks on social media, you'd be much better off asking them to talk in physical environments (as in: "Hey, are you going to XYZ? I think I might, we should hang out at it.").