This is not only true of twin flames, it's true of everyone in your life. Your perception of the people around you is a reflection of you...
When someone's behaviour hits a nerve, when it triggers you, when you have a strong opinion on what they're doing, and have a lot to say about it (even if you're just saying that to yourself) your intuition is trying to get your attention.
It's felt more intensely with a twin flame because it's an all-consuming experience, and your attention is focused on them more than anyone else. So it makes sense that they become your most accurate mirror of what's actually going on within you.
* When they reject you, abandon you, or behave in ways you wish they wouldn't ~ think about how you're also doing that to yourself, how are you rejecting self-love, abandoning your self-worth, or behaving in ways that don't serve YOU.
* When they do or say something that leads you to think 'wow, they really need to work on... their boundaries, their attitude, their self-acceptance, their self-worth, their inner work...' listen to your opinion and turn that around to speak to YOU.
* When something triggers you, hits a nerve, or you have a gut reaction ~ that is your intuition, when something resonates it rings true. No matter how someone else sees it, if it rings true, it's true for you. Pay attention to that.
It's a mindfulness practice really, to be aware in any moment of how your external reality is reflecting something back at you ~ highlighting something you need to learn or explore further for YOURSELF, and it's ALL inner work...