1) That all depends on whether or not she is having an affair. As you yourself just stated above, you need to determine that FIRST, to calculate your best course of action.
2) You will know her sincerity by how she responds to a firm (but loving) legal and/or financial stance by you. If "Ms. Nice-Nice" suddenly goes ape-chit when she doesn't get her way legally or financially, on some initial trial balloon, you'll have your answer.
