Is it permissible for my mother, who suffers from diabetes and has difficulty controlling her urine, to combine prayers to ensure her purity and clarity, even if it is not during the prayer times?

If your mother's urine is constantly flowing, to the extent that she does not find time for ablution and prayer, or if its flow is irregular, then she is considered to have perpetual ritual impurity ( سلس البول ). She must take precautions and perform ablution for each prayer after its time has begun. It is permissible for her to combine two prayers (Dhuhr and Asr, or Maghrib and Isha) at the time of one of them, according to some scholars, such as the Hanbalis. However, it is not permissible to combine more than two prayers, or to combine a prayer that is not to be combined, such as Fajr, or to combine Asr with Maghrib.