Is it permissible for me to agree with my mother to forge a COVID-19 test certificate, knowing that we have lost a lot of money due to the cancellation of previous trips, and that she refuses to undergo testing, claiming she doesn't have money and fears losing what she saved to build a house, and her psychological state is poor?

It is not permissible to obey one's mother in falsifying a medical certificate, due to the forbidden lying and deception involved, as the Prophet (peace and blessings be upon him) said: "Whoever deceives is not from me," and "Whoever deceives us is not of us, and cunning and deceit are in the Hellfire." The mother should be reminded of the prohibition of falsification, and that the loss of money is easier to bear than engaging in forbidden deception.