I think her possession or not of marijuana isn't all that relevant to be honest. The results of her encounter with police completely justify her not wanting to deal or cooperate with them in any way. The exact situation she feared (maybe not, she might have feared worse) did come to pass. It seems to me she had the correct reaction to seeing the police regardless of any amount of drugs she may have been carrying, fear, expectation of violence, and the knowledge that no matter what they did to her it would be excused and waived away with her becoming the scapegoat. Frankly, if every African-American attempted to flee from police in every situation, I'd be hard-pressed to say they were wrong.