Shouldnt it be Rehema ni mwalimu wa mtanzania? I thought you had to put a preposition to connect two? (The "wa" of association, as the hints and tips page says.)
Is this saying she is a teacher of tanzanian or that she is teacher of tanzanian nationality?
Based on the rest of the examples, I'd say it's a teacher of Tanzanian nationality. If it were a teacher of Tanzanian, it would be mwalimu wa mtanzania. Also Tanzanian isn't really used as a noun so it wouldn't make sense, like what would a teacher of Tanzanian teach. Hope that helps!