If your family lawyer agrees, you should have them bring it to the court's attention. Make sure they are aware of the discrepancy and hopefully it will be a benefit to you. Let your family lawyer direct you to whether or not you should present the affidavit to the State Attorney's office. Best of luck.
Any issues not agreed upon in mediation will be decided on by the judge. If you can prove that she lied on her financial affidavit, that will help your cause.
You can use this incongruence in income declared to your advantage when you negotiate at mediation. You should talk to your lawyer about the probability of proving your spouses income in court. The difference is that in mediation you determine your own outcome, and do not take your chances in court. If it looks like it will be difficult to prove her income, you may be better off coming to an agreement at mediation.