Should have, Would Have, Could Have Social Awkwardness. Hind sight 20/20 Help Please?

I'll make this as short as possible. Met & Spoke with a lady today at a school function. Graduated with her husband 20+ years ago. Mentioned that she looked like a girl we (her husband and I) had gone to school with. She informed me that that girl was his old girlfriend. Ooops moment #1. I tried to make light of the situation and said I hadn't known that (i really didn't) and casually asked if she still lived in the area. As a matter of fact, she does and both the old girlfriend and wife are both teachers. Ironic! I chuckled and said well his taste in women didn't change because you two really look alike. Oops moment #2. I shouldn't have said that, I feel like it just sounded foolish. IT GETS WORSE. she said well i don't know if we look alike, she's probably prettier than me. I realize now, that I should have said NO- she's not. because she really isn't (prettier than her) and the old girlfriend clmate girl was hateful, so i could have said "you're nicer and prettier"