She does not need a visa as Kuwait offers transit without visa for airside transits less than 24 hours.
However, as someone who has been living in Kuwait for more than 10 years, I would strongly recommend transit through another airport.
The transit experience in Kuwait is best to be avoided, especially if she is transiting on Kuwait Airways - flights are often delayed or canceled.
The airport itself is not hospitable for transit passengers.
Transit experience is very poor at the airport.
There is the Safir Airport Hotel, and Kuwaiti law mandates that any passenger in transit more than 8 hours is entitled to a free stay at the hotel; however it is not "airside" and you have to be issued a visa to enter. This itself is a daunting process.
The lounge areas (there are three lounges at the airport - the MasterCard Lounge, the Pearl Lounge, and the Emirates Lounge) are okay, but do not provide long term rest areas.
The terminal itself is small compared to its neighbors (a newer terminal is under construction), and can easily get overcrowded.