In case you're wondering it's 表妹.

Also, in case you're wondering why it's not symmetrical (mother's siblings vs father's sisters) is because the complementary set is 堂妹 (younger father's bothers' daughter), and your 堂妹's family name is the same as you.

堂妹's literal translation is "younger sisters living in the same hall" make makes sense when considering how people live together back in the days.

表妹's literal translation is "remote/distant/foreign younger sisters" which you might see them less often in the old days.