Q: Is it permissible for a widow to perform umrah after completing 40 days of her husband's death? Just umrah and nowhere else.
A: A woman in is not allowed to go for Haj during her Iddah. (Fataawa Al Hindiyyah V1 P219). So Umrah during the Iddah is definitely not allowed.
The Iddah period after the demise of the husband is 130 days. She may only leave the house of Iddah thereafter.
Moulana Yusuf Laher