perhaps I can be of some light here.

Rand is an ethical egoist, which means the correct action is the one that benefits the individual. This is different from utilitarianism in that it doesn't matter what is good for others. Only for the individual being considered.

Essentially, if I want Chocolate ice cream I should get chocolate ice cream regardless if my choosing vanilla will provide lots of happiness for EVERYBODY else.

Same for someone else choosing Vanilla, they are not wrong they are just doing what makes them happiest and that is the correct action for them.

The essential problem with Ethical Egoism is it can't really be prooved. when asked the question "WHY? is ethical egoism best" it is tempting to say that when a nation follows ethical egoism EVERYBODY is better off. But thats just silly, because then the theory ceases to be ethical egoism and becomes a convolted utilitarianism in justification. This then begs the question of what about everybody else? Quite frankly we have no reason to judge others over ourself and no reason to judge ourselves over others. This is the essential problem with Rand's view and Ethical Egoism in general.