If a SHY girl teases me, is that a good sign?

So I've been talking to this girl for a while now, it took me a long time to get past her shell, but I seem to be making progress. Like I said, she is quiet and shy with others (a little more outgoing with other girls), she is friendly, talks here and there and giggles a lot but with me she is really "mean" and makes fun of me and teases me and always comments and laughs at whatever thing I say and I've noticed that if I'm with her and there's more people around she is extremely outgoing and people are surprised by her behavior (because she is known to be quiet) and even if other people tease her for whatever reason, she doesn't respond to them or says stuff like "oh you are mean", but if I open my mouth, the barrage begins lol, is this good?
If a SHY girl teases me, is that a good sign?
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