Yes, she used to wear the black frame eyeglasses. But now she wears the contact lenses. If you want to buy the similar one as hers, you could go to the online stores to have a search. There are many similar types. You could go to the ebay or the amazon to have a search.
As far as I know,she has got a very nice vision, perhaps she just try to beautify her looks or she has already used some contacts. However, basically she does not wear eye glasses in order to improve her vision. But sometimes she also try to wear sunglasses which look quite awesome. Since she does not wear eyeglasses, you should try to find your favorite glasses.
Yes, selena Gomez is far-sighted and worn glasses when she was young. But later she worn contacts instead of glasses as she thought contacts are better than glasses on her and she didn't want others see her wear glasses. You can buy this kind of glasses at target or walmart at cheap price.