It's very odd that the police have done nothing. Her XH is committing a crime by behaving like this.
Anyway, she can apply for a non-molestation order – she should call the National Centre for Domestic Violence (www.ncdv.org.uk/) – they can talk her through the process and may be able to refer her to a law firm which will help prepare the papers including the evidence to show why a non-mol is necessary, free of charge. My firm does that and I have assisted on about 15 applications but the referrals need to come through the NCDV.
Alternatively, she could go directly to her local court which deals with domestic violence applications, and complete the papers there herself.
The initial application is made without notice i.e. her XH won't know anything about the application unless the court makes the non-mol order (and it sounds like in this case the court would do so). A judge will usually hear the application on the same day as it is filed or very shortly afterwards.
The non-mol order, application and evidence would then need to be served on the XH (the NCDV can help with this process; often the court serves the papers itself – the applicant must NOT serve them because of the risk of violence by the XH).
There will be a further hearing which the XH will be able to attend and argue against the order remaining in place. Your friend will probably find the prospect of facing her XH in court very scary. However, the court is familiar with this situation, sadly, and will be able to put protections in place to avoid your friend meeting him outside the court room (e.g. separate waiting rooms/staggered arrival times) and may well be able to supply a screen for the hearing room also. She can also take along a relative/friend for moral support. She does not need a lawyer – this process is designed to be done in person but it can helpful to have a lawyer assist in preparing the papers.
A number of my clients have gone through this process: the XH/XP has tried to get the non-mol cancelled but has failed to do so.
You can have a non-mol even if you are having to have contact in relation to children – that is the situation for a number of our clients.
Hope this helps.
Good luck to your friend.