What Causes Swelling In Shoulder?

Hi, My girlfriend her her back in the upper right shoulder posteriorShoiulder. Swelling noted. Has been iced and now heat being applied. It happened at work. She is currently going to a Max center this afternoon. She is also worried about the drug test they give. She only takes Soma and occassionally Abien. Does not do any drugs or on any morphine ect. Two Questions. Drug test? and shoulder? I thank you.