Can my wife cancel my green card?

Relax, your wife cannot cancel your green card. Although, you are a conditional resident and although, your resident status expires May 2015 if she refuses to join you in filing the I-751 to remove the conditions when the time comes Feb 2015, you can file for the permanent green card without her.. You must provide evidence that your marriage was in good faith and also file under one of the exceptions to joint filing. At this time, since it appears your marriage is not working well, you must assume that she will not help you in filing the 1-751 to remove the conditions, then, to be safe, I strongly suggest you should speak to an attorney right away to begin to explore the process of filing the I-751 without her

Since you have already received your residency status, your wife can no longer withdraw her petition for you. She can, however, cause problems by reporting to immigration that you allegedly committed marriage fraud if she believes that you never had the intent to share your lives together and that you entered into the marriage only for the green card. However, immigration cannot accept the truthfulness of her allegations without sufficient evidence to support it. If she refuses to sign a joint petition to remove the conditions on your residency and instead divorces you, you can submit the I-751 petition by yourself and request a waiver of the joint petition requirement on the basis that you entered into the marriage in good faith and that it was later terminated by divorce. To support the waiver, you will need to submit sufficient evidence that the marriage was in good faith.