it means that she don't like or love I think when a person is sad; and he like her so much;

関心がない、彼女のことではないなど場合、使います。 たとえば、「君が行くかどうか、好きにしよう、彼女が無関心だ（She doesn't care）」 複数の場合は「They don't care].

Examples: She don't care [ she does not care] whether you stay here or not. She don't care [ she does not care] whether she lives or dies. She don't care [ she does not care] what you say about her.

Thank you for the answer. It is helpful :)

She doesn't care.......means.......she is not woried. Don't care her............means......don't be worrid about her.