Hi gabrielamaria,
Imitation and Shell Pearls (imitation) can look beautiful and that is generally a glance is enough to scream imitation. Many people love them though so there is no reason why you cannot enjoy them. If you have the receipt for them though or access to the shop itself I would approach the sellers and demand my money back. That was way too much to pay.
But we all live and learn and often by our mistakes. I have trusted photos only to end up with huge shell pearls. I was livid though although I didn't pay much. My mother-in-law loves them.
I think she would be too scared to wear them if they were "real" pearls, come to think of it I might be too. Scared of loosing them that is.
Bodecia