i'm sorry, but i don't understand the problem. you asked for something and your mother got you something even nicer. of course you can wear pearls with jeans and a sweater - in fact, that would look terrific! and nobody can tell if they're real or fake, so if someone is judgmental enough to dislike you for wearing pearl earrings, they would've done so if they were fake as well. pearls are in my opinion a true lady's jewelry, and you can wear them with pride. also, even if you didn't want pearl earrings at all, you should be gracious and thank your mother appropriately, which i have no doubt you were planning to do regardless.
(perhaps i should qualify this by saying that when i was four years old i saved the box-tops from ice cream and sent away for a pearl necklace, which i thought was real for about a year and a half. when i was sixteen, my father taught me that regardless of the occasion a lady always looks wonderful in a black dress and a pearl necklace. and when i got married last june, my mother gave me a pearl necklace that had belonged to her aunt, which i wore at my wedding and frequently since. so it's a bias i pretty much grew up with)