There are no laws prohibiting people from buying vibrators and dildos, but there are laws in some Southern states that prohibit selling them--most notably in Alabama, Mississippi and Texas, where lawsuits against the constitutionality of banning the sales of sex toys have been filed and ultimately rejected. However, the rest of the retail-community in the U.S. can sell vibrators and dildos. They are mainly sold in sex shops, and usually those purchasing sex toys must be over 18 years of age.
If a person is old enough to purchase a vibrator and dildo, doing so through a reputable sex shop will give her the chance to talk to salespeople who are knowledgeable, personable, and willing to answer questions about different brands, materials or anything else pertaining to vibrators and dildos.