Purity: Tayammum Instead of Ghusl After Ḥayḍ
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 463:
If after her bleeding stops a ḥāʾiḍ does not have time equivalent to performing ghusl but she can perform the prayer during its prescribed time by performing tayammum, the obligatory precaution is that she must perform the prayer with tayammum; and in case she does not perform the prayer, she must make it up. Furthermore, apart from shortage of time, if for some other reason her duty is to perform tayammum – for example, because water is harmful for her – then she must perform tayammum and the prayer; and in case she does not perform the prayer, it is necessary for her to make it up.
-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)