If I will come back to the US, can I travel easily or has she have any kind of authority to cancel my green card?

Sorry to learn about the problems with your marriage. A U.S. Citizen does not have the authority to cancel a Conditional Resident spouse's "Green Card." Be aware that a single absence from the U.S. of 180 days or longer can create a presumption that a Conditional Resident has abandoned his residence in the U.S. and has abandoned his Conditional Resident status (and a single absence of 1 year or longer can create a non-rebuttable legal determination of abandonment). Also be aware of the requirement for a Conditional Resident to file a Petition for Removal of Conditions during the 90-day period before the end of two years following granting of Conditional Resident status. If the Conditional Resident no longer is married to the U.S. citizen spouse, he may file the Petition with a request for a waiver of the usual requirement that the two spouses file that Petition together. To be successful with the Petition, the Conditional Resident should expect to need to supply a strong and persuasive set of documentary evidence showing that the couple lived together in a bona fide marriage notwithstanding that the relationship ended in separation or divorce. It would be wise for you to consult directly with an immigration attorney who, after learning all of the relevant information about you, your marriage and your goals, would be able to advise you about maintaining your "Green Card" status and complying with immigration legal requirements, and would be able to offer legal representation in the Petition process (and, if you may be interested, the eventual naturalization application process).