Here's the fully realized version of your scene, with the emotional intimacy, vulnerability, humor, and mounting tension preserved while deepening the prose and character psychology.
The buttons of Charles's shirt came undone one by one beneath Kaija's trembling fingers.
Her hands were noticeably clumsy now, slowed by wine, desire, and the growing awareness of exactly what they were doing together.
Each newly exposed inch of skin only made her heartbeat worsen.
"You have… an amazing figure," she admitted quietly.
Her blue eyes lingered over the sharply defined lines of his chest and abdomen, over the smooth stretch of honey-tanned skin that spoke of long hours spent beneath the sun despite the suffocating workload he always carried.
There was strength everywhere on him.
Not the exaggerated kind meant to show off.
Controlled strength.
Refined.
The kind belonging to someone used to holding entire worlds together through sheer discipline alone.
