Do you think that a 'mistress' should have equal rights as the legal wife?

A lady should never be the "other woman" if she can avoid it. As the third part of the triangle, her position is unfair and unpleasant. She is anathema to the Wives' union. Her family is disgusted with her. Her friends are unhappy an disapproving. Her life is a series of brief encounters with someone else's husband. She is often very lonely. Sometimes she is a better woman than the wife in possession, but she is always regarded as a thief, a fox among the chickens. She lives in constant state of expectation - and depression. "I love you, I hate my wife, I'll get a divorce' is the chain that binds her. She usually accepts the situation at the beginning but as the years go without a change in the status quo, she often becomes as nagging and destructive as the wife he wanted to leave at the beginning of the liaison. The 'other woman' is a fool. In the beginning she gets all what she wanted by a twist of her fingers as she has everything, young and beautiful and 'satisfactory' to her man. As long as he is happy with her, he will shower her with anything that money can buy. She is also known as the 'lady of leisure'(LOL)that ease the job of a wife. But not all good things last forever, he will in the end go back to his wife and children leaving this woman alone and maybe penniless.
Do you think it is fair to be left in a lurch after being in service, filling the job of the rightful wife? Can the 'other woman' seek for compensation when the relationship ends?