Tarabbaʿat is a feminine singular past verb denoting spring residence or pasturing. Tartaʿī is a feminine singular imperfect from r-t-ʿ, “to graze at ease.” The imperfect after the past can make the grazing scene feel ongoing and visible.
Al-Quffayn is a place-name in dual form. Fī al-shawl locates the she-camel among other camels. Reading the sentence as a sequence keeps together the seasonal setting and the vividly continuing act of grazing.