Prohibited Practices for a Mourning Woman
Question

If a woman’s husband dies, she remains in ‘iddah (a waiting period) whilst mourning. What are the things that a woman should not do during the mourning period?
Praise be to Allah.Forbidden practices for a mourning woman : 

Go out of the house : she is only allowed to do so for a necessity, such as if she is sick and needs to go to the hospital, in which case she should go during the day; or in the case of emergencies such as if her house is about to fall down and she fears that it may collapse on top of her; or in the case of fire; and so on. 

The scholars said: “She may go out during the day for necessary purposes, but at night she should not go out unless it is essential.” 

Wear perfume: the Prophet (peace and blessings of Allah be upon him) forbade the  mourning woman from wearing perfume except when she purifies herself following her period, in which case she may apply a little Azfar (a kind of perfume) after her period ends, to remove the traces of menstruation odour
Wear beautiful clothes : the Prophet (peace and blessings of Allah be upon him) forbade the woman from wearing clothes that are considered to be adornments while mourning. Rather she should wear ordinary clothes such as the kind that she usually wears inside her house, without making herself look beautiful
Apply kohl: the Prophet (peace and blessings of Allah be upon him) forbade that. If she needs to use it, she should use the kind of kohl whose colour is not obvious, applying it at night and removing it during the day 
Wear jewellery : if a woman is forbidden from wearing beautiful clothes while mourning, it is more appropriate that jewellery should not be allowed. 

Permissible practices for a mourning woman:
It is permissible for a widow in mourning to:

Speak to men 
Speak on the telephone
Allow people to enter the house who are permitted to do so according to Shari`ah
Go onto the roof of her house during the night and during the day. 

Practices women are not compelled to do during mourning:
There are some practices that women commonly do while mourning which they are not compelled to do, such as:

Perform ghusl every week as some of the common folk think
Undo their hair every week
A widow in mourning does not have to – indeed it is not prescribed for her to – go out when her `iddah (waiting period) ends and give charity to the first person she meets. This is an act of bid`ah (religious innovation). 

And Allah knows best.