Good question and happy to oblige.
You're on the right track with Blue Man Group (Venetian). Lighting, props, projectiles (the first few rows are called the "poncho section;" the audience wears plastic ponchos for protection), and a vast amount of paper are employed to great effect in this show. It does incorporate music, but it's mostly percussive, so perhaps your sister can feel, rather than hear, it. Best of all, the three Blue Men are mute, so the show relies not at all on dialogue or sound bites.
For our money, though, the greatest spectacle in Las Vegas is KÀ (MGM Grand). Here, again, there's no dialogue, and the music is dispensable. All the impact of KÀ is visual: the massive hydraulic stage that moves in ways you simply won't believe; the whiz-bang special effects; the fabulous costumes and amazing sets; the pantomime and physical feats; the sight gags; etc.
All the Cirque du Soleil shows, in fact (with the exception of LOVE, set to the vital Beatles music, at the Mirage), are recommendable, as the Cirque dancers, acrobats, clowns, contortionists, and other performers speak no words, relying instead on strange sounds that are incidental to the performance. Mystère (TI), O (Bellagio), and Le Rêve (Wynn) all fit the visual bill.
If you're (or she's) into male beefcake, the performers in Chippendales (Rio) and Thunder from Down Under (Excalibur) are known less for their witty repartee and more for their bowties, white cuffs, spandex pants, and other physical attributes.
Folies Bergère (Tropicana) and Jubilee! (Bally's) are old-school Vegas production shows, heavy on staging, sets, showgirls, special effects, costumes, and dancing.
And the magic shows, such as Lance Burton (Monte Carlo) and Mac King (Harrah's), are possibilities. Though there's some verbal comedy in Mac King and Lance Burton mumbles a lot, the sleight-of-hand tricks and large illusions need no verbal explanation.
Note that most of the shows in Las Vegas offer assistive-listening devices, so if your sister has any hearing at all, she could be helped by the aural enhancement. Inquire at the box office when you buy your tickets.
