Well, I don't want to offend you or your friend but your friend is ignorant. She obviously has no knowledge about curly hair, so her comments are somewhat unintelligent. If you have curly hair and you put a perm in it or a relaxer then it will not of might not be healthy because you only put chemicals in your hair, so the comment of your friend telling you to put a perm in it makes no sense at all. Besides, let her know that you like your hair, it's your hair not hers, so she should get off your back.
Everyones hair can be healthy, curly hair is more fragile than straight hair, but that doesn't mean it can't be healthy.