Yes, she did. He got it mixed up and repeated something like "Laci did know" and Diane said, "No, did Amber know?" And he answered that Amber did not.
Thinking again about this, it is another proof of his lying because even if for some unfathomable reason Laci agreed to let him keep seeing Amber (HIGHLY UNLIKELY), I think Laci would never have stood for the fact that SP was still stringing Amber along with the "unmarried" lie, not wanting to lose Amber if she knew he was married. That basically says to Laci, "I don't care about you and your feelings, but I DON'T WANT TO LOSE MY NEW HONEY."