Dear Mr. Kreuger,
Thank you for posting your request on History Hub!
If Christine left the United States and gave up her US citizenship, there should be expatriation records that the Department of Homeland Security (DHS) would maintain. However, she would not have been required to give up her US citizenship, therefore, if she decided to maintain her citizenship status DHS will not have her records.
If this is the case, it would just be her passport that would indicate her travel from the United States. It is also possible that DHS could have passenger manifests for vessels and airplanes departing from North America during the 1980s.
Since Christine is still living and the emigration actions occurred so recently, it is unlikely that a third party would have access to any records that might exist. We suggest you try submitting a Privacy Act Request Submission Form through the Department of Homeland Security.
We hope this is helpful. Best of luck with your research!
[Information provided by Elizabeth Burnes, Subject Matter Expert]