That her father (Abu Bakr) never broke his oath till Allah revealed the order of the legal expiation for oath. Abu Bakr said, "If I ever take an oath (to do something) and later find that to do something else is better, then I accept Allah's permission and do that which is better, (and do the legal expiation for my oath ) ".  

أَنَّ أَبَاهَا كَانَ لاَ يَحْنَثُ فِي يَمِينٍ حَتَّى أَنْزَلَ اللَّهُ كَفَّارَةَ الْيَمِينِ قَالَ أَبُو بَكْرٍ لاَ أَرَى يَمِينًا أُرَى غَيْرَهَا خَيْرًا مِنْهَا إِلاَّ قَبِلْتُ رُخْصَةَ اللَّهِ وَفَعَلْتُ الَّذِي هُوَ خَيْرٌ  

Abu Bakr As-Siddiq had never broken his oaths till Allah revealed the expiation for the oaths. Then he said, "If I take an oath to do something and later on I find something else better than the first one, then I do what is better and make expiation for my oath."  

أَنَّ أَبَا بَكْرٍ ؓ لَمْ يَكُنْ يَحْنَثُ فِي يَمِينٍ قَطُّ حَتَّى أَنْزَلَ اللَّهُ كَفَّارَةَ الْيَمِينِ وَقَالَ لاَ أَحْلِفُ عَلَى يَمِينٍ فَرَأَيْتُ غَيْرَهَا خَيْرًا مِنْهَا إِلاَّ أَتَيْتُ الَّذِي هُوَ خَيْرٌ وَكَفَّرْتُ عَنْ يَمِينِي