Liz, unless you want to make some stops along the way, you should look into taking the train or flying from Granada to Barcelona. There is an overnight train, and you'd probably want to get a sleeper compartment. However, I did quite a bit of research on this for my upcoming trip.

Iberia Airlines is the only airline that flys non-stop between the two cities, and the one-way airfare is grossly expensive - 207 Euro. However, I was able to get a ticket for 125 Euro. Turns out the roundtrip fare, with a Saturday night stay comes to 133 Euro, and if you become an Iberia Plus frequent flyer member (no charge, and you can do it online), book online, and purchase an e-ticket, you get an additional 8 Euro discount, therefore costing 125 Euro. Just toss the second leg in the trash after you claim your luggage.

There are 3 direct flights a day, one at 9:45am, one at 1:15pm, and one in the evening, about 6pm. The flight is only 75 minutes, and to save time, its worth the cost of the flight for me. I don't recall what the cost of a sleeper compartment is on the train, but it wasn't that cheap either.

Hope this information is helpful.