Hello, I went through your query, yes it is due to sitting for long time on the same posture, hindering venous drainage from legs causing swelling, and pain. It came be avoided by taking regular break from, walking around for 1 or few minutes frequently, adding daily exercise to her routine,, like brisk walk, jogging, squates, aerobics,, strengths her leg. If overweight she needs to reduce weight. Eat more of fresh fruits and vegetables. If not releaved even with this please consult physician.