Sally Bercow, already on a list of those who wrongly named or linked former senior Tory Lord McAlpine with child abuse claims, sent a message on Sunday night to her 59,000-plus followers asking what happened to teacher Jeremy Forrest, 30, and reportedly named the girl.
The tweet was later deleted after Mrs Bercow was apparently warned about the order by journalists.
Today people trying to access Mrs Bercow's Twitter account were met with a page saying: "Sorry, that page doesn't exist!"
An order has been made under Section 39 of the Children and Young Persons Act 1933, banning identification of the girl.
The order states: "Any publication by whatever media in breach of this order is punishable by a fine in the sum of £5,000 (€6,200)."
Sussex Police, the investigating force in the Forrest case, said: "Sussex Police is fully aware of reporting restrictions around the case involving Jeremy Forrest and, therefore, is being cautious in the information we release.
"We will actively investigate potential criminal breaches of these restrictions by others."
Scots-born Forrest, a teacher at Bishop Bell C of E School in Eastbourne, East Sussex, was arrested in Bordeaux in France on September 28 after a European arrest warrant was issued.
He was charged with child abduction after being extradited, and at his latest court hearing he was further remanded into custody at Brighton Magistrates' Court to face a committal hearing at the same court via videolink on December 3.
It is the second time this month that Mrs Bercow's use of Twitter has resulted in potential problems for her.
On November 4 she tweeted: "Why is Lord McAlpine trending? *innocent face*."
She is accused of linking Lord McAlpine with a BBC Newsnight programme which made unfounded allegations of sexual abuse against a senior Tory at a children's home in Wales.
Mrs Bercow has defended her tweet, describing it as not libellous but "just foolish".
The outraged peer and his lawyers did not agree and his solicitor Andrew Reid confirmed that Mrs Bercow's name was on an extensive list of those against whom legal action might be taken.
She responded to suggestions that she would be contacted by Lord McAlpine's lawyers by taking to Twitter again, posting: "Thanks for phone calls/texts/tweets.
"I guess I'd better get some legal advice then.
"Still maintain was not a libellous tweet - just foolish."
On Sunday she tweeted that she was "a bit scared to comment on trending topics nowadays".
And she told her followers that she does "not have the money to contest a multimillionaire".
Media law specialist Mark Stephens, a partner with law firm Finers Stephens Innocent, said he did not think Mrs Bercow had broken the law.
He said: "It seems to me that everyone is treating her as if she is mainstream media.
"But, in fact, she is only using her memory. Her tweet was not a report of the case, it was a comment.
"Even if she was technically in breach of the law - and she would have had no knowledge of the reporting restriction order - there would be no public interest in a prosecution. She cannot un-know what she already knew."
Mike Dodd, legal editor of the Press Association news agency, said: "Mrs Bercow might not, in fact, face the risk of prosecution, or, if she does, should have a defence.
"Section 39 of the Children and Young Persons Act 1933 makes it an offence, punishable on summary conviction by a fine of up to £5,000, to publish a report of the proceedings in court which includes information calculated or likely to lead to the identification of any juvenile covered by the order.
"If Mrs Bercow's message was not a report of the relevant court proceedings, it is difficult to see how she could be said to have committed an offence.
"Section 39 orders are not intended to give an individual juvenile anonymity in relation to anything other than the relevant court proceedings."