Depart from Beetletun and progress to the beach as indicated. As you get closer you can hold down the ALT key to see the missing children and some of the Mantle. Pick off the surrounding groups of hostile Mantle. If you are close enough dialogue will begin to play but Lovisa and those with her remain in a confined area. Once the surrounding groups have been cleared, Lovisa can be attacked directly. This can be a challenging battle, but it is possible to pull Lovisa or others from the area, which both lowers the numbers you face at a time and prevents the children from applying their benefit.