As stress get the centre stage these days the curious question of the body and mind comes in to play again and again. Often the holding or tightness that people experience in their body is not a physical symptom but a psychological one. A student may face a challenge much greater then solely having sciatic pain, however it is also a tricky situation of timing to know when is it the right opportunity to make the shifts needed to experience change. I understand your concern with encouraging her to stay with a Restorative practice even though she is craving a more vigorous flow style however you may want to consider the Bhava or feeling of the practice instead of the actual postures. If you use sequencing that allows for rest and integration as well as time for her warrior nature to shine through, in essence creating a Satvic or harmonious practice for her she may be more able to begin the journey towards transformation. By continually encouraging her to notice the difference between engagement and relaxation she may awaken to the concept that for a muscle, cell and psychological pattern to shift and truly experience peace and strength it needs to know and have felt the difference between the two.
Use the Bahva or intention of what yoga truly is, as stated in the Yoga Sutras of Patanjali, yoga is the mind which no longer identifies itself with it’s vacillating waves of perception and that all yoga asana are meant to be steady and comfortable. Or consider working with your student from the perspective of divine love and encouraging her to see herself as divine, without needing to fix or change anything simply allowing herself the space to become aware of her true potential.