have you talked to your spouse about it? maybe, she/he may not want to be stay in this marriage without her child. A lot of people look out for their children's happiness as well, not just their own.
Plus, by the time that child comes to the States, it's going to be time for her to go away to college at 18. She may not be living with you all that long.
Neither my husband nor I thought that my parents would ever live with us. We were used to living on our own for a long time. They immigrated to the US, lived with us for about 2 years on and off, and now they live separately, so everybody is happy, and everybody is in the States. A temporary inconvenience is just that - temporary.
Other than that, revoke it by writing to USCIS where it's pending.