Is it illegal to make a fake facebook account pretending to be someone they are not?

This is against Facebook's policies, so anyone complaining should be able to to get the account disabled, and possibly the friend's real account as well.

California has recently passed a law which prohibits impersonation of another on the web. 528.5. Credible impersonation of actual person on Internet Web site or other electronic means; penalties; civil relief; other prosecution Currentness (a) Notwithstanding any other provision of law, any person who knowingly and without consent credibly impersonates another actual person through or on an Internet Web site or by other electronic means for purposes of harming, intimidating, threatening, or defrauding another person is guilty of a public offense punishable pursuant to subdivision (d). (b) For purposes of this section, an impersonation is credible if another person would reasonably believe, or did reasonably believe, that the defendant was or is the person who was impersonated. (c) For purposes of this section, “electronic means” shall include opening an e-mail account or an account or profile on a social networking Internet Web site in another person's name. (d) A violation of subdivision (a) is punishable by a fine not exceeding one thousand dollars ($1,000), or by imprisonment in a county jail not exceeding one year, or by both that fine and imprisonment. (e) In addition to any other civil remedy available, a person who suffers damage or loss by reason of a violation of subdivision (a) may bring a civil action against the violator for compensatory damages and injunctive relief or other equitable relief pursuant to paragraphs (1), (2), (4), and (5) of subdivision (e) and subdivision (g) of Section 502. CA PENAL § 528.5