Has she actually committed a crime though?
The Criminal Justice and Public Order Act 1994 inserted Section 4A into the Public Order Act 1986. That part prohibits anyone from causing alarm or distress. Section 4A states:
(1) A person is guilty of an offence if, with intent to cause a person harassment, alarm or distress, he— (a) uses threatening, abusive or insulting words or behaviour, or disorderly behaviour, or (b) displays any writing, sign or other visible representation which is threatening, abusive or insulting, thereby causing that or another person harassment, alarm or distress.
and
The Racial and Religious Hatred Act 2006 amended the Public Order Act 1986 by adding Part 3A. That Part says, "A person who uses threatening words or behaviour, or displays any written material which is threatening, is guilty of an offence if he intends thereby to stir up religious hatred." The Part protects freedom of expression by stating in Section 29J:
Using the term "final solution" really only has one intention in this case, and it's to stir up religious hatred and violence.