Единственный недостаток тети в том,

Единственный недостаток тети в том, что она не очень тактична и не умеет разумно тратить деньги.

Результаты (английский) 1:

The only downside to my aunt that she is not very tactful and doesn't know how to spend money wisely.

Результаты (английский) 2:

The only downside to my aunt that she is very discreet and does not know how to spend money wisely.

Результаты (английский) 3:

the only disadvantage of aunt is that she is very gentle and can reasonably spend money.