In shiʾta means “if you wish.” Its repetition frames two contrasting outcomes: lam turqil (she does not hurry) and arqalat (she goes at a fast trot).
Although shiʾta is formally a past verb, the conditional particle gives the statement a conditional meaning. The two alternatives emphasize one consistent feature: an animal responsive to direction. The rhetoric depends on parallel structure and contrast, not on a contradiction about her speed.