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.
A menstruating woman who intends to perform Hajj or Umrah should perform all the Hajj or Umrah rites except Tawaaf (circumambulation around Ka'bah). In fact, she should not perform Tawaaf unless her period stops and then she performs Ghusl (ritual bath). So, when your wife in her menses reaches the Meeqaat with the intention of performing Umrah, she immediately enters the state of Ihraam and stays in that state avoiding all things that are unlawful for the person in state of Ihraam like perfume, …etc. Now, when her period stops and she performs Ghusl, she can perform Tawaaf and any remaining rites of Umrah. But if her menstruation starts after she enters Makkah and after performing Tawaaf, then she completes the remaining acts as we mentioned earlier. The evidence for this is the Hadeeth that the Prophet said to Aa'ishah when she menstruated: "Do everything the person who is performing Hajj does, but do not performTawaaf around the Ka'bah unless you become pure". Allaah Knows best.