Number of Transit Visas Required

[immihelp]

I am travelling on my British Passport and so do not need a visa. My wife, who will be travelling with me, has a Dominican Republic Passport. Your web pages say she needs a Transit Visa. Does she need two visas? One to stay for a few hours at JFK for a flight to the UK ( she has a UK visa) and then another to travel back through JFK to home to the Dominican Republic?

[immihelp]

One visa if she can get transit visa for the entire duration of your trip.
Otherwise, two visas.