“The body language of crossed arms is negative.”
Can also be interpreted as “I mean business!”
No matter how it’s stated, the body language is not warm in that photo. Maybe, as you indicated, Melania wanted to convey an “I mean business” vibe with it. As a former model, she knows how to pose for different effects. The photo just isn’t my cup of tea, as mentioned not only for her crossed arms, but because of the busy background. My preference is for warmer images.