Is it permissible to lie to one's grandmother about the price of an expensive medicine, and give it to her at a reduced price, knowing that she will not accept financial assistance?

Fear of lying and eagerness to honor your grandmother, Mahmud, are commendable. Lying is forbidden and among the ugliest of deeds. However, in such a situation, one can use allusions (ma'areedh) and double meanings (tawriya) instead of lying to achieve the desired outcome. Allusions are sufficient for a Muslim to avoid lying. Tawriya means that the speaker intends a correct meaning with their statement, which is not a lie from their perspective, even if it appears to be a lie based on the literal wording. For example, one could say to the grandmother, "I paid (so much) for this medicine," stating a low amount, while intending that this amount is only part of the price.