She could be pregnant, but she also might not be. The only way to know is to take a pregnancy test. You can't keep this from "getting worse", she's either pregnant or she's not at this point. Nothing you can do can avoid it. You may consider a visit to planned parenthood to get help understanding your options if you do get a positive test result.
Since she had already missed a period, she should be able to take a pregnancy test and get an accurate result.