Is it permissible for a woman to take pills to prevent the arrival of her menses so she can perform the rites of the Hajj or Umrah with ease?

I do not see any harm in a woman taking this medical treatment, with the condition that the doctor in his/her professional opinion does not see any harm for the woman in taking these pills.

So, the basic principle in these things is permissibility, and so long as there is no falling into sin in this act.