If he wants to earn her trust, research her past and the asshole who scared her into who she is today... AND F'n buy a home for the other lady! Make it obvious to EVERYONE whom the >main< woman in your relationship is and who is just a friend.
It's the ambiguous situation that makes it appear as if Valerie is just entering as a concubine/side hoe. That's why she herself is believing it herself. There's already a confident woman in your home, in your life, on a first name basis whom can come and go when she pleases... in a society where only the WIFE can do that.
ML is feeding into her trauma like hand feeding koi in a koi pond. All she can see is the sword above her head, trying to see where the deathstroke is going to take her from.