Cardi B and Stefon Diggs were caught on video in a heated argument. The incident happened on Wednesday afternoon (May 13) outside of a coffee shop and gym in Burtonsville, Maryland, according to TMZ. Video obtained by the outlet showed the rapper seemingly yelling at the NFL star while he stood leaning against his sports car with his arms crossed. At one point, a man accompanying Cardi stepped in and placed a hand on her as if trying to calm her down. Although the audio in the clip is inaudible, TMZ also reported that a source overheard Cardi say, "That bitch is messy," though it was unclear who she was referring to. The outlet also said the argument lasted at least 10 minutes and security turned away fans hoping to get Cardi's autograph while the dispute played out. The public clash came just days after the two appeared affectionate together at Diggs' Diggs Deep Foundation Mother's Day event.…