All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
If the questioner is able to perform the Maghrib prayer after coming back home, or at the place of the course before the time of 'Ishaa' starts, then it is permissible for her to attend this course. However, if attending this course will lead to delaying the Maghrib prayer, then this is not permissible. Allaah Says (what means): {Indeed, prayer has been decreed upon the believers a decree of specified times} [Quran 4:103], which means that the prayer is prescribed on a very specific and determined time from which one cannot delay it or advance it except for a valid reason, and studies are not a valid reason for combining Maghrib and 'Ishaa' prayers.
We do not think that attending the course and performing the Maghrib prayer on time is impossible. It is possible for her to perform the prayer at the place of study; she may choose an appropriate place and perform the prayer before the starting of the course or immediately afterwards and before the time of 'Ishaa' starts. She may also take five minutes from the time of the lesson and perform the prayer and then resume the course, so there are many solutions she may find, especially that her mother is attending the course with her. If her mother is a Muslim, then they can alternate in performing the prayer. One of them may go pray while the other is attending the lesson, and when she comes back from the prayer, the other may go, and at the end of the lesson each one would explain to the other what she had missed. So there are many solutions she may think of instead of thinking to delay the prayer from its prescribed fixed time.
For more benefit on the ruling of combining the prayers because of studies or exams, please refer to Fatwa 86594, and Fataawa 83812 and 84024 on performing the prayer at the place of study.
Allaah Knows best.