Why does she get mad at another girl?

So Saturday i was out in town.
I am talking to this girl I am into, i believe her to be into me. We had kissed a couple of times.

But as I was talking to her another girl said hi to me and called me Maxi. My name is Maximilian, so it is quite common for people to call me that.

But the girl I liked felt like this was special for us and gets pissed at this girl. ‘Why the f*** do you call him that’ she asked surprised.
I was surprised by her reaction.

I later asked her about it because i said you know it is common for people to call me that and she said she really overreacted and just felt like it was personal for us.

Now today she texted me: about what happened this weekend don’t think I am super into you or anything, I overreacted.

I feel like she is really into me: acting like i am hers, saying she loves me, even kisses and misses me.

But now she pushes me away like it was all nothing and it ‘just happened’

Why does she get mad at another girl?
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