A rival

I dunno why but someone just pointed on me and suddenly said: "YOU're My RIVAL!!"
it took me by surprise,seriously...
I don't even understand a word she said O.o
Does that mean I get an enemy??
...
That's definitely not good...
and I think I've met her before....
without a doubt,that face looked familiar...
who might that be?
I need to remember soon,or else...