Is it permissible for my mother, who works as a doctor and finds it difficult to pray on time due to busyness and her slow movement, to combine the Dhuhr and Asr prayers with an early combination (Jam' Taqdeem)?

A Muslim must perform prayer at its appointed time, based on the Almighty's saying: "Indeed, prayer has been decreed upon the believers a book [due at] fixed times." Combining prayers is not permissible except for a legitimate excuse, such as travel, illness, fear, or rain. A mother's preoccupation with her work does not permit her to combine prayers. Rather, she must perform the Asr prayer at its appointed time. If the time for prayer enters while she is treating a patient who might be harmed by her delay, then she may delay the prayer until the end of its time.