Colleague A started in our team around 3 years ago. She has an uncommon first name and we asked her at the start how to pronounce it and she told us. I've heard her on the phone and interacting with other staff hundreds of times and we say it the same way she does.
Colleague B started about four months ago and when introduced to A, she said 'isn't your name pronounced XYZ'. Colleague A said no, she says pronounces it ABC. B said she knew someone else with A's name and insisted it was XYZ.
B continues to pronounce A's name the way she thinks it should be (its quite different to what the rest of us are saying) and frequently corrects the rest of us when referring to A. We have spoken to A about it but she's very non confrontational and says she doesn't mind B's insistence and doesn't want to speak to her about it. B has quite an aggressive personality and has been prone to outbursts in the office a few times in the short while she's been with us so nobody is really sure what to do.