How do i know that my teacher is talking bad about us to other teachers?

I constantly find her talking to a teacher and suspiciosy looks at us. When she is with another teacher, i smile to them and neither one gives me a smile back...they give me this weird 'yea...thats her....' face that freaks me out. Once my principal (i had been like her favorite student since like forever btw) suddenly yelled at me saying "Gosh i feel like im talking to myself!" an im like "hu?" and she said "dont go near the clrooms!" and i just walked away from the clroms. i saw my friend coming and i took 3 steps back and started walking again. then this other teacher said "Brenda, i dont wana tell you again" (btw she completely forgot about the girl that turned back with me!) my teacher was like next to her and started talking again. And to all of the teachers...she calls them to talk to them and she talks to them and looks back @ us like saying 'thats them' if she is talking trash about us, (btw..again...we dont cause much trouble in cl)then how do i stop it?! help!!!