Tahani’s defining characteristic is Envy, which makes her a Heart Type. After that, discerning whether she’s a Two, Three, or Four becomes difficult. She has traits that fit into any of those Enneagram numbers.
The interesting choice is a Two. Her impulse toward charity work is genuine, even though it begins as a way to prove to her parents that she’s just as worthy of love as her sister.
She’s very successful at raising money for a cause, which could make her a Three. She’s also very emotionally connected, a Four possibility.
Ah, but she considers the morale of the neighborhood to be her responsibility. This is a Two. A Four would take more personal time. A Two won’t rest if they think they can help others. Also, that self-sacrifice convinces Tahani that she’s a good person. A Two, one of the most giving numbers of the Enneagram, can avoid introspection if their work is deemed to be important. Her own motivations, something she will eventually need to examine in the Good Place, are constantly set aside so she can uplift the community.