I would have waited, personally, until I had some solid other relationships rather than when you're in the newbie dating stage trying to figure it all out yourself, but you already told her, so...
Did she ever know or find out about the affair you had?
You could pose it to her that way, you know, like: "Would you rather see me having an affair in secret and deceiving my husband, sneaking around so my children don't know where I really am? Or isn't it healthier to be honest and open with each other about what's going on?" And then be firm, "Look, I know this is something you object to, but I feel you are not making an attempt to understand. My husband and I love each other and have made this choice knowingly and willingly, and I would like to know I have your love and support even though you do not approve."