Is it legal for a bank teller to check friend's accounts without reason?

My friend is a bank teller and she had an off putting habit of checking my accounts for no reason. She would watch it and call me if I had overdrafted, which I admit was nice I guess, but still a little weird that she would be checking it without me asking. Given her nosey nature, I'm pretty sure she checks the accounts of other people she knows as well. Is this legal or ethical? To abuse the power to be able to spy on people's financial situation and spending habits? I have since changed banks for that reason (among others), but I was curious about this. I don't have anything to hide but I don't want people going through my personal records when it's not their business to do so.