To be fair, using your argument it would also be short sighted to join a union just because your current boss sucks. The next one might be awesome and now you’re paying dues for nothing.I do think her reasoning for not considering a union is short-sighted. Goodness knows there are plenty of examples of employees being exploited by employers. Just because she is not encountering that, right now, has no bearing on what is happening elsewhere and may come to her place of employment.
For the record, we were at that Starbucks to show solidarity. We entered, placed an order, and when asked for our name, replied "Union Strong". After a few orders under that "name" were filled, the manager prohibited the baristas from calling out that "name". After we left, one who did so, was fired.