“Intransigent,” meaning stubborn and unwilling to compromise. It’s similar to “adamant,” but has the additional sense that the person is perhaps being inflexible just to be stubborn or contrary, and not for any firmly-held belief.

Example:  “Although Jamie had already won the arguments over child custody and support payments, she remained intransigent in her insistence that her ex-husband also pay for all of the school uniforms.”