Hi, I hope I can offer some help with your question. From the information you have provided, you initially were attracted to her romantically, and developed your relationship on the basis that it might lead to a romantic relationship. It does sound as though she has deliberately negated to disclose her married status to you at this time, it seems others were aware of her being married, and she had clearly shared this with them.
Clearly you have a bond, and this is impacting on your ability to seek and sustain a relationship with anyone else, whether deliberately on her part or not, this is giving her the best of both worlds at the moment, a husband, and a b-friend, while leaving you in a more vulnerable situation.
The thing that stands out here is that her deliberate vagueness leaves her open to deny that she is doing this to you - that she may be keeping you stringing along, and putting your life on hold for her, without her having to acknowledge this to you, or even admit it to herself. It might be helpful to consider whether this is really what you want for yourself and your life? Clearly you are good friends, have a special bond, and have strong feelings for each other, but have you considered whether this is really in the friend zone for either of you, if it is preventing you from having a relationship as well. Do you think her husband is aware of you, and as is likely the case, if not, how do you think he would feel if he knew?