Because of its previous wounds that recently healed and the amount of blood she have lost, the mermaid is taking a while to wake up. According to the witch, she estimated that the mermaid might wake up around 2 to 3 days later. It will take some time before her body managed to recover fully but considering she lost quite a lot of blood, the body will naturally let the body to rest and increasing the time of sleep to repair everything and replenish what was lost is usually the main reason why one who got injured and bleed out a lot will take sometime before they wake up.