Yes.
Focus on being the best, the most capable, dominant, and sexually satisfying man and leader she's ever had.
You'll know when she's checking out of a relationship for real, if you're honest with yourself. She'll be difficult, she won't chase you or need you, she'll complain, she'll push back, she'll be irritable, she'll avoid investing in you, she'll be unenthusiastic about sex, she'll not take opportunities to be with you, etc.
But if she's focused on you (and you're doing a good job in your role) she's following you, adapting to you, looking for ways to please you, seeking your attention, being submissive to you, hovering around you, wanting sex with you, giving you choices over her life, trying to implant herself in as many different ways as possible into your life, and making herself psychologically and sexually open to you.
It's very hard for a woman to properly submit to two men, in fact she's designed specifically not to do that. She can pay lip service to one dude while she's in love with another, but she can't be in love with and open herself completely to both. But if a guy's idea of what he should expect from women is a relationship where he's trying to please her every step of the way even while she's ambivalent or disrespectful to him (as is the modern concept of relationships these days), then her paying him lip service is not incongruent with those expectations. So she could be pining after (and even fucking) someone else and the relationship would be fully up to the standards he's been given. Don't be that guy. Set high standards, high enough that it would be difficult for her to accept them if she wasn't committed.