My dear
@lexy , let me tell you a phrase that I learned years ago during my economy classes that has stuck with me for years:
"As long as there is demand, there is supply"
Just because a certain activity isn't popular or, for that matter, known by more than a small percentage of people, doesn't mean that there won't be people willing to pay money in order to obtain items that allow them to indulge in that activity. Tea drinking is simply impopular, not prohibited.
It's a similar case to having a sex shop in the middle of the town: sure enough, nobody will be willing to admit to entering a sex shop or, for that matter, buying any of the items inside of it, but the shop will still be conducting business
for a reason.
Luckily for our heroine , in this case it's not an activity as, errr, "morally reprehensible" as outdoor bdsm or displaying a dildo you just bought. Tea drinking is a foreign activity that is not well known in the country yet, is not in vogue, competes directly with the current popular activity (coffee drinking), has some kind of bias associated to it ("humpf, if this ia drunk by those foreign brutes then it must be a drink for brutes too"), its full potential has not yet been realized and, most importantly of all, it has yet to make a place for itself in the most pedantic, biased, backstabbing, vicious, entitled and overall nasty place of all: the high courts, where our beloved heroine lives, interacts and generally bases her knowledge from.
So yeah, it's an uphill battle, but not a forbidden one.