Custody papers

My ex went on IRS web to check refund status with my ss#, is this illegal? I think it is. I have one child with her (8) and she has one child(10) , this child thinks I'm her farther and only knows me as her dad, I have claimed her on my taxes every yr for about 8 yrs with my exes consent every yr, I did it again even though we have been split for about a yr, now the tax return was two weeks late getting to her and she is mad and say I was not supposed to claim her daughter, when she said I could , now she is saying she is gonna get me for tax fraud, when thus is not the case. Verbally was the way it was consented like always, can she do anything! I think she is all talk, what do you think she can do to me, she is treating out of anger