My mother is very busy with her work at the office. She still takes good care of us.

My mother is so busy with her work at the office that she cannot take good care of us.

Because my mother is very busy with her work at the office, she takes good care of us.

In spite of being very busy with her work at the office, my mother takes good care of us.

My mother is too busy with her work at the office to take good care of us.