Re: The Rights of Women in Islam
Up to 1/3 of the total estate can be given to whomever the parent wants, as stated in a will. Typically this is charity, but it can just as well be a needy daughter.
Does it bring it up to “equal”? That depends on the circumstances…it may even be more at times.
The rules are quite complex. This article has a few interesting scenarios:
http://weekly.ahram.org.eg/2000/491/li1.htm