I dated an opposite religion lady for two and a half years. But due to her father disapproval, she decided to end the date. I decided to go on another date with another lady but later find out that the former lady intend coming back. Should I take her back

IF you can be convinced as close as possible to 100% that her father will not be an interference again.

No. Religion is one of the biggies in life, and it really should not be ignored.