She claims that he is strong, tender, attentive, and loving and that he speaks his mind. What she is not facing is that he is also dishonest. He is, after all, cheating on his wife. If he'd cheat on his wife while they were in a committed relationship, there's no reason for Natalia to think it would be any different if he was in a relationship with her.
Is he really speaking his mind? Is he speaking his mind to his wife so that they can work out the problems in their relationship rather than him cheating on her? Is he really speaking his mind to Natalia when he says he loves her? When you love someone, you support their highest good, and he isn't supporting Natalia's highest good by being involved with her.
Words are easy. It's easy for this man to say he loves Natalia and to be tender, attentive, and loving in an affair. Narcissists are often absolutely wonderful in affairs, but obviously, if he were a man of integrity, he wouldn't be having an affair.
If Natalia does her inner work and learns to love herself, then she will have a much easier time letting go of this married man. When she loves herself, she will want to be with an honest man, a trustworthy man of integrity—not a man who cheats on his wife. She will realize that it is very unloving to herself to be involved with this man.
If Natalia learns to love herself, then her underlying fears of rejection and of engulfment can be healed. When she develops a loving adult self who is capable of not taking rejection personally and capable of not losing herself in a relationship, then she will be available for a committed relationship with an available man. As long as she is with an unavailable man, she doesn't have to worry about losing herself in a relationship—which is likely the fear that is keeping her from being available.
If you find yourself drawn to emotionally unavailable people, people who are married, or people in committed relationships, then I suggest you explore your own fears of being in a committed relationship. It's likely that your fears of rejection and/or engulfment are keeping you from being available. The good news is that you can heal your fears by learning to love yourself.