I think there's more motive here than we realize. the negro was also involved in a home invasion.     the negro already said she thought the woman was rich. most likely looking for an old ladies purse to snatch to get her address then rob her house. this was a clear prelude to a home invasion. given that she's small and weak, she's looking for even weaker targets: old white women.    if they hadn't caught the negro, that woman would have most likely had her home robbed as a result -- possibly even killed.