A girl from my class called me a keyboard and told me I had a big mouth but small balls. What did she mean by that?

If i insult a girl from my class online and she tells me to say it to her face to face but i refuse. And she then goes on to call me a keyboard warrior and say that i have a big mouth but small balls is that a very clear indication that she believes that she's physically stronger than me and that im afraid she's gonna kick my ass?

A girl from my class called me a keyboard and told me I had a big mouth but small balls. What did she mean by that?
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