No.
Private companies can require any skill they so wish from a prospective employee before they get hired, they are after all private companies, and every level of government may need people who can communicate in a wide range of languages. In that case, they can require proficiency in a foreign language as a pre-requisite of employement. If your relative was hired for a job that required a certain level of proficiency in Spanish, and she can't perform at that level, then the employer has the right to terminate, if that's not the case, she needs to get a good attorney, and sue the pants off that school district.