Fiancée only throws up from dark liquor

Hi all,

My (29M) fiancée (26F) seems to have issues only with dark liquor. I pointed it out months ago and she stopped drinking dark alcohol and had no issues and tonight accidentally had some potential dark rum and is throwing up again.

Wondering if this is actually a thing — a specific insensitivity to dark liquor and nothing else that causes vomiting — or if something else is going on here.