Is it permissible to delay making up the Asr prayer for several days or weeks after becoming pure from menstruation, before Maghrib, and only perform the Maghrib prayer upon ghusl?

It is obligatory for a woman to perform the ritual bath (ghusl (definition)) immediately upon ascertaining purity, and not to delay it until the prayer time expires. This is the preponderant opinion. What the questioner does by delaying the ghusl is an error, and she must make up the prayers she missed due to this delay. This making up (qada') is an immediate obligation.