There are several considerations for your friend – firstly how to transport her horse to France and then, how to keep and look after it here and, of course, making sure it is legally registered.
There are different options for bringing the horse over including using her own horsebox (if she has one) by ferry. She should check with ferry firms to make sure this is possible and if there are any specific requirements; certain routes do not take horses and in other cases they only take a fixed number at a time.
Another option is via the Channel Tunnel, using one of their approved transporters, see eurotunnel.com/uk/traveller-info/pets/horse-travel
Finally you could go for another transport company equipped for horses which would take the horse in a large horsebox via ferry (air transport of horses exists but is very expensive). Expect to pay around €1,000 or more to a transport company.
In France all horses must be registered with the SIRE, a central database of horses present on the territory (Système d’information rélatif aux équidés).
To do so requires an EU horse passport (there is a charge of €240 for horses without an EU passport), which your friend should already have, a declaration of ownership, a €95 cheque made out to IFCE (see below) and a stamped addressed envelope.
For more details, including declaration of ownership forms (in English) to download (see on the right-hand side) visit: ifce.fr/ifce/sire-demarches/au-cours-de-la-vie-du-cheval/importation/
If your friend needs somewhere to keep the horse, she could look into écurie/s (stable/s) or une pension de chevaux. The following site is useful: pension-chevaux.com Tariffs vary depending on how the horse is accommodated; if food is provided etc. The body should be set up as a business with a Siret number and have assurance responsabilité civile professionnelle. Riding centres (centres équestres) sometimes offer pension facilities. You can find more about owning a horse from the Fédération Française d’Equitation (ffe.com) and Institut française du cheval et de l’équitation (ifce.fr).