Reading between the lines (from interviews, her intermission feature at Les Troyens, her past reviews, etc.), I'm surmising that Elza van den Heever found this Elizabeth a stretch dramatically, having generally played "nice girls" in her still-young career ("sweet," as she said), and ultimately resorted to extreme measures (no doubt with the director's collusion or suggestion): the shaved head, the imitation-Bette-Davis swagger in the walk. And it sounds like she didn't succeed in making the latter her own.

Kay, as I'm sure you know as a longtime operagoer, for the first half of the 20th century the "serious Donizetti" was an ignored repertory. Lucia was the sole exception as certain star sopranos found it (after some adaptations) a congenial vehicle, but otherwise the common "wisdom" was that Donizetti's style was suited only to comedy; I remember reading exactly this in a midcentury history of opera. The exploration of this literature that gained force in the 1950s changed this situation, but operas like this one are still laboring to gain some familiarty.