Well, I’m not sure exactly, but it was a test to make sure she was sober. A breathalyzer would be kinda stupid for LE to request, because it would be easy for her to not drink alcohol until after the test. A UA that detects alcohol as well as other substances makes more sense to me, because usually the conditions of being released on bond require the person to abstain from any alcohol or drug use. Plus, a UA would detect things used over the past few days whereas a breathalyzer alone would only indicate alcohol use in the immediate hours before the test.
I’ve worked in corrections and all the people I saw come in on probation violations, etc., that were caught using something were caught by a dirty UA.