Can anyone help me identify what kind of dog my brother has?

My brother has had her since 2019. She is about 6 or 7 years old. He got her out in Riverside, CA. All we know is that she's mixed with an Australian Cattle as she is always nipping at peoples ankles lol. Her teeth are little but they are a bit sharp. She's only aggressive when people walk up to our front porch and she sees them.