My nephew left his girlfriend and we were seeing his daughter on the weekends since she was a baby and bought her clothes, pampers, wipes and necessities but when we befriended his new girlfriend the baby's mom forbid us to see the baby anymore and we miss her dearly.

Do we have any rights at all?

Sorry, but you do not have any legal rights in this situation at all..

Sorry no, but on the days that your nephew has the child you can visit the child when your nephew has the baby with him