Is the mother right in her concerns about naming her daughter "Rahw" because the name appears in a verse that speaks of drowning and torment, and there is a disagreement over its meaning?

Your concern is valid, as the name "Rahwa" has several meanings, some of which are not suitable for naming a girl, and she might even be taunted because of it in the future. Therefore, we advise changing it to names of the Mothers of the Believers and the righteous female companions, such as: Fatimah, Aishah, Khadijah, Maryam, or Zaynab, and similar names that have no religious prohibition.