Basically, there two sets of laws were enforced under Ptolemaic rule, one Greek, one Egyptian. Under Greek law, a woman required kyrios. She could own and manage property, but could not make major transactions without his consent. She could, however, petition the government without his involvement if necessary. Egyptian law was not so restrictive. Women did not need a guardian and could make property transactions on their own. They were, however, expected to consider their own interests less important than those of a husband.
The thing is, these laws did not apply separately to each respective group. Over time, less in the earlier period, more later, Greek women began to take on more of the Egyptian model. They began disposing of common marital property and managing businesses when their husbands were traveling, only asking permission for transactions after the fact.* Sonless, widowed mothers gave their daughters in marriage. In short, Greek women began taking on aspects of Egyptian law and custom that granted them a little more freedom.
Part of this came out of the contact between two sets of laws and the fact that, within certain limitations, many Greek women were able to take advantage of some of the freedoms granted under Egyptian law in their own lives. This was helped along by the reality that they no longer had a polis to protect and regulate their lives. Without those safeguards, Greek women had to have more economic and legal freedoms, if only to protect themselves and their family’s property.
*Though it is important to note that they still asked for transactions to be approved, just afterwards instead of before.
Pomeroy, Sarah. Goddesses, Whores, Wives, and Slaves: Women in Classical Antiquity. New York: Pantheon Books, 1995.
Johansson, Nathalie. "Women in Egypt - how the status of women in Egypt changed during the Ptolemaic Period." Dissertation. 2010. Academia.edu [Link is here]
Pomeroy, Sarah. Women in Hellenistic Egypt: From Alexander to Cleopatra. Detroit: Wayne State University Press, 1990.