Being an immature adult toddler

I'm at the age now where I expect all the older adults I work with to be mature and professional. But I couldn't be more wrong! The longer I work with people that are older than myself, the more I see how childish they are. I've been dealing with a coworker for the last two years that is the most immature, unprofessional person I've ever dealt with. She's essentially a toddler boss that throws temper tantrum. She thinks because she's in a position of management she gets to do whatever she wants. She's also not from the US, which I think plays a part in how she thinks things are run.

She often bullies me, which probably sounds dumb but that's because it is! Like the fact that she goes after me so often, about things that aren't even real or important is pathetic. She allows her own team to do whatever they want, which includes being unprofessional, rude and disrespectful, lazy and irresponsible. But as soon as someone else does that, or basically goes after her team at all they become a target.

This person has repeatedly come after me and my job. She makes me life very frustrating sometimes. Just today she claims that one of her employees claims I was rude to them. In an interactions that lasted about a minutes and a half which involved me explaining how something worked and answering all their questions, apparently was just me brushing them off and ignoring them. Which is pretty funny since just last week one of her employees not only ignored my emails but hung up on the phone with me in the middle of me speaking to them! Yet no repercussion for that?

It's just so funny to me that someone that is twice my age is actually a bully. Like didn't we leave that shit in middle school? At every new job I've had, I hoped that the crowd would be more mature but that seems to not only be untrue but this is the worst I've ever experienced.