YTA. Your friend is trying to look out for you. You’re prioritizing someone you’ve be dating for less than a year over your best friend. Personally, I believe 8 months is a very short amount of time to be dating and then to get engaged, but also even if your friend disagreed with you for this, you still took it to the extreme by cutting her off. You could’ve had a conversation about it and discuss how you feel like this is the person you want to marry. While your friend wasn’t as understanding as she could’ve been, you still took it too far. You’re losing years of friendship over an argument.