Oleta is probably a variation of Alida, which comes from the Latin word aliger which means "winged" or "having wings". The "a" on the name is a diminuative, so the name means something like 'little winged one' or 'little bird'. Alida also has a Hungarian/English/Germanic definition on this website.
Deleta must come from the Latin deleo/deletum which means "to destroy", so the name means 'the destroyer' or 'little destroyer'. That might seem like a harsh name... but it seems to me that it could have been taken out of context from a bible or sermon. Regardless, destruction isn't always bad... you can destroy bad things as well as good. I guess if you were willing to make a stretch with some really questionable spelling, it could also come from a name like Delicia.