I want to first acknowledge what an important and challenging question this is. Most people have experienced a “difficult” or “unfair” boss at some point in their lives. There is a lot of advice (often contradictory) on what to do about it. Ultimately, it is important to handle any situation in a way that you’re comfortable with. Here are a couple of ideas that might help.
One way both parties in a mentor-mentee relationship can hold each other accountable is through documentation. Having a record of decisions, conversations, feedback, etc. can help both people identify (and hopefully avoid) miscommunication. A lot of frustration can arise from misunderstanding each other. Ideally, your mentor would have a system in place to incorporate this. If not, this is something you can ask for. For example, you might mention you have noticed miscommunication and ask if they would review/approve your meeting notes, or communicate major updates via email. If they are still not amenable, reach out to your program or other resources to help generate a plan.
Unfairness is also a difficult experience; we’re programmed to notice differential treatment. Sometimes, differences are necessary and helpful. Perhaps your lab mate needs accommodations, or your mentor is training an academic hopeful differently than someone interested in industry. Sometimes differences arise from prejudice and ignorance. It is important to evaluate the situation and try, to the best of your abilities, to see if there is a reason for the unfairness. Communication can help here too. It is reasonable to ask questions about how mentorship is being handled. For example, “I’ve noticed another trainee in the lab attends many conferences. I am interested in attending more conferences. What would make me eligible to also attend?” Approaching the issue in a direct, but non-confrontational manner will likely lead to greater success.
The mentor-mentee relationship is unique and challenging. Both parties have expectations of themselves and the other that are sometimes misaligned. Some PIs may not recognize that they are being perceived as difficult or unfair, whereas others may see it as a means to an end. The best way to deal with conflict is to make a plan, approach the topic professionally and politely, and above all, communicate. Mentorship is often seen as unidirectional, but the mentee is also responsible for directing the relationship. And if you still have trouble, it may be time to ask for help.
I want to add one final note. I opened by acknowledging most people have experienced difficult or unfair bosses. But I want to be clear: no one should experience abuse, harassment, prejudice, or bullying in the workplace. If your experience is more severe than a difficult relationship, please use your institutional resources to get help. Everyone should be welcome and safe at work.