Is it permissible to give the price of a mobile phone that was bought from a wealthy relative at a low price, and she forgot that she sold it, to the needy, instead of giving it to her, in order to avoid family problems?

It is obligatory to pay your aunt the price of the mobile phone, and it is not permissible to give it as charity to the poor under the pretext of fearing that your aunt might suspect she has another debt. A way can be found to repay the debt without embarrassment.