getting ears pierced at any age.. its going to hurt! no way around that!!
If your daughter wants them done and you are willing to let her, than that is all that matters. You know that you are going to be the one who cleans them and help her take care of them, if your up to it.. then let her do it.
The only difference now between a younger girl/ older girl and one your daughters age is she is going to want to mess with them more.. so you will need to remind her more often not touch them until they are healed.
This is a personal choice you have to make about your daughter and you are the only one who can decide wether its a good idea for your daughter or not.. you know her best.
Good luck to you and your daughter on your choice! :)