What is the ruling on naming a newborn girl 'Ola, Malak, and Ayah?

It is better not to name a female "Malak" (angel). There is no harm in naming her "Ayah" or "Ula". The general rule regarding naming is permissibility. A name is only forbidden for a valid legal reason, such as if it is exclusive to disbelievers or wicked people, or if it contains a forbidden or legally blameworthy meaning.