Sylvie Guillem has been very clear about her desire to retire from dancing while the pleasure she takes in her work outweighs the physical pain. Yet it still seems incredible that Life in Progress is to be the last show of her career – with her flukily beautiful limbs and transparently expressive technique, Guillem at 50 can still dance almost anyone else off the stage.

It’s typical of her stubborn integrity that the farewell programme she has chosen is more about risk than nostalgia. All four works are by contemporary choreographers, two are specially commissioned, and if some of the new material turns out to be an illuminating challenge for her, some – almost inevitably – is less than perfect.

There’s certainly a mix of both in Akram Khan’s Technê, a very private incantatory solo that’s dominated by the silver, tree-like structure around which Guillem circles. The choreography thrums with ideas and emotions yet, as can be the case with Khan, some of the imagery lacks clear theatrical focus. At its best, however, Technê opens up startling views of Guillem’s talent, and there are certain movements – a fast scuttling crouch in which her bent legs vibrate like dragonfly wings; ferocious, flung gestures that retreat abruptly into firefly flickers – that are so extraordinary, they defy physical logic.

Russell Maliphant’s Here and After, in which Guillem is paired with the excellent Emanuela Montanari, also has its disappointments. The opening section feels like Maliphant in default mode, its slow, stretchy sculptural movement occupying familiar terrain. But the second half becomes a complete blast as Maliphant unleashes a dazzle of deft, jiving partnerwork, arcing limbs and skittering turns that unites the two women in a bold, teasing and very female complicity.

Guillem takes a breath while Brigel Gjoke and Riley Watts perform William Forsythe’s Duo, a piece of outstanding brainy beauty that I’d love to have seen her dance. But she’s back on stage for Bye, the quirky, mercurial solo that Mats Ek created for her back in 2011, which portrays her as a middle-aged woman, dancing alone with her memories.

It’s a solo in which Guillem’s dancing is at its most musical, most intelligently charismatic, but it ends with her being summoned away from her solitary performance by a crowd of (digitally created) family and friends. As she leaves the stage, she turns briefly to face us with an expression that hovers somewhere between resignation, hopefulness and pain. For us, as for her, it’s an unbearably apt final image.

• Until 31 May. Box office: 0844 412 4300. Venue: Sadler’s Wells, London.