Your question is quite general and hence it is difficult to give you a framework of what you are asking for. There are individual differences that exist and these must be kept in mind. More importantly one has to understand the perspective within which you are wanting to understand the nature of introverted women. The best thing to do would be to assess your relationship with the specific individual. Here are some simple tips may help you judge this for yourself. First establish a friendship with reasonable boundaries and slowly bring in personal issues that are not of high significance. Assess to what degree the person is able to respect these issues. If the level of comfort is high and you feel ok you may open up the communication further and tell her that other issues that you may share with her are likely to be more serious and you would appreciate if she could respect the confidentiality. Finally you may want to observe what references she makes to other people and how much she shares about them with you. If she is transparent then that may indicate that she is an open person so you can decide what and how much to share with her. I will however reinforce that these are not exhaustive ways of understanding
anyone but might give you some leads.