Hi! Two things. 1.No cafe should be steaming coconut or any nut milk as it can trigger anaphylaxis. Lactaid and rice milk should be fine, though. We did it at the Starbucks I worked at.
2. PSL is probably gluten free, however the SPICE they put on top sometimes is probably NOT gluten free. The barista won't always put it on top which may be why you'd react...