Can she get temp residency and find a way to continue to live in the US without me?

I found communication between my wife and a girlfriend that she married me just for papers and plans to leave me as soon as she gets residency. I have confronted her about the letter but she says she just wrote that in anger and does not have those intentions. Meanwhile, I continue to see more evidence of her true intentions. Will she be successful in doing this? Can the letter I have be used as evidence?