you feel weak and afraid and are afraid that her response will be one of anger toward you - and she knows that you are afraid to confront her on issues now, she has the power in this relationship and she can do whatever she wants.
Not pursuing legal separation or divorce at her end means that she wants the exciting single life, the thrill of the fantasy but in case it doesn't work out, she likes having the security blanket of a marriage and a husband who will ALWAYS love her and take her back if she decides to come back. The problem is that when they have all the time in the world to make a decision, do you think they will make a decision now or later about the marriage and if she takes as much time in the world to make a decision, do you think she will want to come back or do you think she will get used to living the carefree, no responsibility single life that you are furnishing for her?