Help with Ishtar

Unless you plan on using your units competitively, I don't think it should matter.

You could patch up her loss of Atk by using a +3 Atk seal, but you lose your seal slot.

You could run Life and Death 3.

You could hold onto this Ishtar until you eventually get a better one.

Or you could fodder off her skills to another unit.

She has good fodder

Do you really want to use her? If not give Odd Attack Wave to Linde. Or Tharja. Or Nino.