Bro to bro: a woman's loyalty is not to you. Her loyalty is to what you represent. It's hurt to hear but it's the reality.

Your character, purpose, ambition, standards, your ability to lead yourself, people around you, provide, and protect. The luxury, calmness and comfort that come from being around you. The status, class, and social hierarchy.
When you remain consistent in what you represent, her loyalty will be yours forever. When you're epileptic, disrespect, loss of attraction & desire, cheating, divorce, etc., become the endpoint.