Did she lie in any way in that B2 application, saying, for example , she was married? Or that she had kids back home?
If she didn't lie, it might be ok.
Like others have said, stop listening to anyone that tells you that you need to lie to immigration. Lying is never ok, but especially in immigration since sooner or later, the truth comes out and just because you're fine in this stage, it doesn't mean it will not come up in the future. Especially because there is usually more than one application that you will file (in your case, K1, then AOS, then ROC and then maybe citizenship). So you will be with immigration for the next few years.