My friend who I treated as my sister suddenly become unfriend with me , she think that is a step to move forward in life , I feel sad that she just walk away without saying goodbye.

Dear friend, I can understand how difficult it must be for you to suddenly lose a friend who you considered as your sister. It's natural to feel sad and hurt when someone you care about walks away without saying goodbye. You may be feeling a range of emotions such as confusion, anger, and sadness. It's important to acknowledge and validate these emotions as they are a natural response to loss. From a Buddhist perspective, everything is impermanent, including relationships. As much as we would like for things to remain the same, change is inevitable. It's important to recognize that this is a part of life and that we can't control everything. We can only control how we respond to it. It's also important to practice compassion towards yourself and your friend, understanding that everyone is on their own journey and that sometimes, people need to move on in order to grow. From a psychological perspective, it's important to process your emotions and thoughts around the situation. It may be helpful to talk to a trusted friend or therapist about how you're feeling. It's also important to avoid blaming yourself or your friend for what happened. It's not uncommon for people to outgrow relationships, and it's not a reflection of your worth as a person. You can also practice self-care by engaging in activities that make you feel good, such as exercise, meditation, or spending time with loved ones. In terms of coaching advice, it may be helpful to reflect on what you learned from the relationship and how it has impacted your life. You can use this experience as an opportunity for growth and self-reflection. It's also important to set boundaries for yourself and to avoid reaching out to your friend if it's causing you distress. Focus on building new relationships and engaging in activities that bring you joy.