Adoption and Divorce HELP!

What is the name of your state? Indiana

OK...I adopted daughter July 02 I have basically raised her since she was 3 yrs old (now 12). Problem is my wife has filed for divorce in Jan 03 (she is having an affiar) and I have found out that she was possibly with this guy in July. I feel I was set up. I will always support my Daughter emotionally and financialy. However what can I do to my wife for lying to the evaluator that came to our house and asked tons of questions including how our marriage was and my wifes response "great/awesome etc". She told her mother that she was seeing him then and told my MIL what was I supposed t say "do not adopt my daughter cause Im having an affiar"? My MIL response was yes. My wife denies this conversation took place (duh) with her mom but can I do anything against her law wise. In other words make her pay for her lies WITHOUT reversing ADOPTION. I do not want my daughter affected.

Jeff