Upvote:2
She can apply for a visa from the Netherlands (at a VFS Global office in London, Edinburgh, or Manchester) or France (at a TLScontact office in London and Edinburgh). Those links will have all the instructions and forms to fill out.
She should apply to the country that is the main destination for her first trip. If she receives a multiple entry visa, she can use that for subsequent trips to the Schengen area as long as she doesn't exceed the dates and number of days limitations on the visa and the 90/180 days rule.