Boulaz began climbing in the Alps in the 1930s and continued making major ascents until the 1970s. Of her major climbs, four were the first ascents and at least nine were the first female or all-female ascents. At the start of her career, Boulaz and Lulu Durand became the first women to climb the Dent du Requin (1932) and the southwest face of the Dent du Géant. She made a number of climbs with Durand in 1935: the first female traverse of the Aiguille des Grands Charmoz; the first female traverse of Les Droites; the first female ascent of the north face of the Petit Dru (with Raymond Lambert), and the second ascent ever; the first female ascent of the Central Spur of the Grandes Jorasses; the Aiguille Noire de Peuterey; and the Brenva Face of Mont Blanc. She was the first person to climb the east face of the Bel Oiseau (1938), the north face of Mont Vélan (1941), and the Rothorn of Valais (1941). She was the first woman to climb the Pear Buttress on Mont Blanc's Brenva Face (1939), the Walker Spur of the Grandes Jorasses (1952), and the north face of the Cima Grande di Lavaredo (1960).