Is it good for a 7month old baby to get her ears pierced?

No. I've seen young children with pierced ears whose earlobes have been torn during rough play with siblings. Metal allergies can be an issue, and if improperly fastened, the child may pull off and eat. I counsel my parents to let their children decide if they want pierced ears when the child is old enough to care for it themselves.
Neither. Its not good or bad, as long as its done by qualified person, and cared for in proper manner, should be fine, actually better than when theyre older and more afraid.
Neutral. It is neither good nor bad. It is purely cosmetic and to enhance your enjoyment of your child. I would strongly recommend you seek out a pediatrician that does ear piercing using sterile medical plastic studs with decorative tops. Mall earring studs have many metal components and are not sterile. This leads to the potential of infection and metal allergies that will haunt the child for life.