My daughter has an anxiety disorder and depression (officially diagnosed, takes medication). One of the ways these manifest themselves is an inability to give-and-take, relax, "go with the flow" kind of attitude. She's intelligent, and she knows what ought to be done, but she can't seem to just let things roll off her back.
For example, our car is a newer model and if you're driving at night with the headlights on, when you get home and turn the engine off, the headlights automatically turn themselves off. No more forgetting to turn them off, thus draining the battery. My dh uses that feature (I am old-fashioned and in the habit of turning them off), and it drives our dd to a state of anxiety, agitation and near-panic. She knows the lights won't stay on. She understands the technology perfectly. But she can't bring herself to get out of the car unless the headlight switch inside the car is on "off". And she would scream at us, and every car ride when my dh was driving would end with dd being so angry.
She also is very aware of what's fair and what isn't, even though she comprehends that in some cases, fair just isn't possible. But it upsets her inner scale, or scorecard, or something, and it gets her quite upset.
She sees a counselor, and we actually - all three of us (dh, me and dd) - had to visit the counselor together to help resolve the headlight issue. It was that bad.
The counselor has helped dd to think of a specific question. In this case, it's "is this a safety issue or is this just something that is bothering me?" In other words, is it like forgetting to turn the stove off, which would be a cause for concern that she should speak up about, or is the headlight issue simply something that affects her and nobody else, since the headlights turn themselves off? And if it's just her, she needs to tell herself in very specific terms, this is not a safety issue, or a case of someone being in danger, and I need to acknowledge that it bothers me but not in a way that makes me become rude to my family or to myself. Your dd may need a counselor's help, or maybe you could help her yourself. You can help her develop a question she can ask. For example: "is this situation something where someone is being treated unfairly due to their race or disability or other quality? Or is this something that bothers me but is pretty ok and normal, like friend A was on the swings for 6 minutes and friend B only had 4 minutes, but they're both happy. So what words can I use to tell myself that it's a real feeling that I have, and I am proud that I have the sense that I do, but I don't need to let it make me unfriendly or rude". Of course, you wouldn't use those exact words, I didn't write them very well, but hopefully you get the point. Which is, acknowledge that your dd's feelings are real, but that they don't always have to be pointed out to everyone. Kind of like listening to a friend's karaoke singing, where you really think she's not very good at all, but she's having a blast and everyone is clapping along and having fun and so you keep your feelings to yourself, and they are valid feelings, but to your friend you simply say "that was so much fun and everyone was having such a great time!" It would be altogether different if your friend was singing karaoke and people were mocking her and she was being humiliated. Then you stand up for her or with her.
Bottom line: help your daughter learn to respect and acknowledge her personality and feelings, but help her learn how to recognize when to keep them to herself, and when to stand up and say "you're being unfair/mean/cruel and I will come to my friend's defense with kindness". Helping our daughter to learn this distinction has been helpful and has made things a little easier around here.