My MIL secretly tested my breast milk for alcohol

My MIL watched my LO while I had the stomach flu. Later that week she gets my husband alone and tells him she tested some of my breast milk for alcohol for some reason. Never said if it was positive or not, I think just trying to start fights. Mind you, I only pump when I am at work and sometimes at night before I go to bed. I occasionally drink a glass of wine with my husband after the kids are all asleep, so any alcohol that might be in the milk would be miniscule as whatever is pumped is always mixed up among the sessions of that day. Am I crazy or is my MIL way out of line? Feel like a trust has been totally broken. I don't want her alone with out baby any time soon.