She is Raj's first daughter
Why isn't it should be "it is Raj's first daughter".
It should accept 'eldest', I think.
No, it should not accept 'eldest' because Raj's eldest daughter would be राज की बड़ी बेटी.
This is the first daughter of Raj. It is also correct. Duolingo do not have much sense. It is only a craming app
Shouldn't it be "elder daughter"?
‘Elder daughter’ would be बड़ी बेटी. पहली means ‘first’, and so there is a simple translation.