Is there anything she must do other than seeking Allah's forgiveness (Istighfar) and repenting for the sin of abortion, which she committed to relieve her husband and out of mercy for the fetus, knowing that the abortion took place in the second to last week of the fourth month?

Abortion is forbidden by Sharia. Its prohibition becomes more severe and the crime greater if it occurs after the fetus has formed. The matter becomes even more serious after the soul has been breathed into it, because it is the killing of a soul that Allah has forbidden to kill except by right. The Hadith states that the fetus forms after forty days, and many scholars have held the view that aborting a fetus is absolutely impermissible. Therefore, the statement that abortion before the fourth month is not forbidden is incorrect. If the abortion occurs after the formation [of the fetus], the direct perpetrator is liable for blood money (diyah) which is inherited by the fetus's legal heirs, and the direct perpetrator of the abortion does not inherit from it if they are an heir. The direct perpetrator is whoever directly carried out the abortion, such as the doctor, the husband, or the woman herself.