The word "loyal" can be defined as "giving or showing firm and constant support or allegiance to a person."
Can you still be characterized as "loyal" if you are not consistent with this trait and constantly showing loyalty? The answer is no. You can't pick and choose when you want to be loyal to someone. It's the same situation as if a person said they are "vegetarian," but only eat meat when they go to their favorite restaurant...you can't be a half-vegetarian. So that means you can't be considered a loyal friend if you are not consistently proving yourself to be one.
What does it mean to be a loyal friend? Even if they don't agree with your decisions, they are able to keep an open mind and see where you are coming from. Even if they don't agree with your decisions, they don't judge you. Even if they don't agree with your decisions, they support you. Why would they do this even though they don't agree with you? Because loyal friends are helpful, not hurtful.
Even if your decision is not the one they would choose, they are able to recognize that you are happy. Loyal friends want to see you happy. They are selfless in recognizing that your happiness is more important than being closed minded. They are happy seeing you happy.
Loyal friends defend you, even when you are not around. They are consistently bringing you up, even if others try and bring you down. They are not tarnishing your name or reputation. We all know our friends' secrets and the skeletons they have in their closet, but why would we expose any of that? A friendship is a type of relationship. The beauty of a relationship is sharing something between two people. That doesn't mean the two people plus everyone else you open up your mouth too.
Have you ever been in a fight with a friend? Have you ever been tempted to speak badly about that friend, just because you are feeling angry towards them at that moment? You think that venting to a third party will be your fix. Words can never be unheard after they are said. You can never take back a negative or regretful comment you make about your friend. If you are not able to recognize that loyalty is still a characteristic to hold even when you are fighting with your friend, then you are like the half-vegetarian.
Just because you and a friend are fighting does not mean it is okay to speak poorly of them out of anger. I believe that words come back around. Even if you think there is no way that your friend will find out what you said, you are wrong. For this third party to allow you to speak poorly of a friend, means they are not loyal themselves. So what makes you think they are going to be "loyal" and keep your regretful words between you two? If someone is talking bad about another person to me, that says more about me, even if I don't contribute to the negative comments. If you do have anger or negative comments built up towards this friend, then they can be voiced to that friend.
Do you think you qualify as being a loyal friend? Did you think you were loyal before this, but aren't really sure now? Being loyal is a trait and virtue. Like all virtues, loyalty can be practiced. Strive to be a loyal friend.