WASHINGTON — She has perfected a mean forehand, is working on her yoga poses, dishes with girlfriends over brussels sprouts and dirty martinis (one olive) at the Mediterranean hotspot Zaytinya, pushes her two daughters to play two sports — one of her choosing and one of theirs — and said this week that the wonders of modern dermatology, like Botox, are in the realm of possibility for her.

Michelle Obama is in many ways the embodiment of the contemporary, urban, well-heeled middle-aged American woman. She likes to take “me time,” as she did during an extra vacation week this month without family in Hawaii, setting off a tabloid furor over the state of her marriage. She frets that her older daughter, 15-year-old Malia, hangs out with the boys a grade above her. She gardens, although unlike the rest of us, she has significant weeding help.

She toys with false eyelashes.

On Saturday night, Mrs. Obama will celebrate her 50th birthday (which falls on Friday) with dancing and sweets throughout the state floor of the White House, drawing the nation’s attention away from her husband, at least for an evening. Guests will sip fine American wines, consume delicate macarons and be entertained — the expectation is by Beyoncé.

Image Mrs. Obama at the White House kitchen garden last spring. Credit... Christopher Gregory for The New York Times

The mix of Hollywood and quirky individualism (American caterers, ready yourself for the onslaught of dessert-and-cocktails-only party requests) underscores the conflicting diptych of glamorous mystery woman and regular PTA mother that defines America’s first lady. Five years in, she has cobbled together a full life in Washington.