How can I tell if my dove is happy?

I have three birds one mourning dove with half a wing and two white doves.They all share a cage and they seem happy.But I feel bad for my mourning dove because she can't fly and she is also missing a toe.I rescued her after she was attacked by a cat.I bought the two white doves to keep her company.They all coo together every morning and evening.They get time outside the cage together and they sit on the same perch together.They are by a window and see the other birds outside.Lily is what I named the mourning dove and I've had her for over a year now.She acts just like a tame bird now she'll sit on your shoulder and will hop on your finger.How can I tell if she's happy.