Irene isn't characterized as any of these things in Passing. To the contrary, she is characterized as reasonable, level-headed, not interested in stirring up trouble, eventually calm and tolerant in even the most trying situations as is shown in Part 3, Chapter 4 when she allows Clare to come into her home and visit with her husband Brian even though Irene knows of Clare's affair with Brian.
It is Clare who is characterized as something of each of your options: selfish, mentally unstable, a woman of her times. Clare is selfish in the way she continues to draw Irene into her sorrowful, confusing life. Clare is selfish for allowing a affair to develop between herself and Irene's husband. She defines herself as at least somewhat mentally and emotionally unstable as she describes herself as someone who will do anything--anything--to attain her goals. A chilling cast is out upon this self-description because Clare also says she does not have a proper moral sense.
Clare is also a woman of her times because her life exemplifies some of the modern social and moral dilemmas that faced black women. Socially, acceptance was limited within the whole society to a subset of society: a dilemma faced each as choices had to be made as to how to negotiate self-respect and limited social respect. Morally, opportunities arose that had been more limited in previous eras: a dilemma faced each as decisions had to be made about moral and ethical behavior in the face of opportunities that took advantage of other people, like Clare taking advantage of Irene and of her own husband from whom she hid her ancestry.
This, she reflected, was of a piece with all that she knew of Clare Kendry. Stepping al- ways on the edge of danger. Always aware, but not drawing back or turning aside. Certainly not because of any alarms or feeling of outrage on the part of others.