Thanks for your prompt reply. Are your friends willing to keep the hotel in Seville for a night while they stay overnight in Granada? I mean, it's a very attractive destination, beyond just the Alhambra. They say Bill Clinton still talks about his Junior Year (or whatever it was) there. I'd want to eat dinner in a "Carmen" restaurant overlooking the Alhambra.
You did not give your full itinerary. Are you staying anyplace closer to Granada, like Madrid? Do you have a night in Jerez? I would certainly give that up for a night in Granada. I don't mean to say what are the best cities in Spain, but I think it may be convenient to take a train between Madrid and Granada. (It is hard to recommend that two people we don't know, or even know their travel history, should make this trip independently. Not that it's a "hard" trip, it isn't.) We did this by rental car, and thought the Canola and Sunflower fields were pretty darn scenic. But the car let us stop and sleep in Ronda, the second place in Spain that people ask you about, after the Alhambra! And there are no sunflowers in the fall.
I like keeping the same hotel and making daytrips, ideally up to an hour each way. But I see Granada as too far from Seville.