wild guess but she probably liked him or/his art.
and the dad and brother are just bad people lol at least the dad is, gayle just didn't want his brother in danger so he set him up with helen
It will be explained later why exactly she married James, and why Gayle sold his brother.
Spoiler:
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she married him to recover the embezzlement money from the children's cancer foundation she stole in order to buy ML from Gale and free him from the mercenary (military) contract.
Like why? She said everything belonged to her, like she was the richer one, so then why did she marry him ? And why is the both the brother and the dad so shitty? One sells off his sibling, and the other doesn't care if his son dies of alcohol poisoning.