Can she cancel child support?

My boyfriend pays child support for one kid to his x-wife, she cheated on him when she got pregnant with her 2nd child and my boyfriend thought it was his kid up until he was born looks nothing like him AJ has blonde hair and my bf has dark brown hair, so he left his wife when he found her in bed with another man, now he pays child support because they live in another state. she just texted us saying she will cancel the child support all together IF he takes a DNA test to prove my bf wrong that AJ is his son and if Curtis is right that AJ is not his son then she will drop the child support, my question is can she do that, I heard no one can cancel it that you have to pay until the time is up on the order like when he graduates from HS or turns 18 and Skyler (the one who is being paid for) is only 8, my bf still has 10 years to go. I think his x wife is just saying this just so he can take the test and she thinks its his son, Its really more he say she say, and I believe my man 100% even though i was not there when she cheated on him or if she even cheated on him, its a really messed up situation, I just want to know if she can do that.