Neither. I try to structure my schedule - more or less around low crowds. As others have kind of said, seeing MK on a super busy day doesn't make for the ideal.
The second thing I learned when planning for a first timer is listen to your friend! I don't know your friend, but if she's all about MK, nothing else will much interest her until she sees it. In which case, hoppers might be great. I'd also say this is a BIG fault of the Brave New WDW- it locks guests into plans- which bites for situations like yours.
Ignore crowd predictions! MK is generally worst on Saturdays. It is great on Sundays. It is also great after dark during warm months. In your case, hopping might really make sense. (if remotely in your budget) I highly suggest doing MK after dark. Ideally, you should be in the parks early (without making anyone miserable), take an afternoon break - and use as many NIGHT hours as you an manage. (SEE BELOW)
You friend doesn't know the highlights of the parks, to her- things you may think are less exciting- will be very exciting, because they are NEW. Her needs trump all else! encourage according to your experience, but don't force anything. Explaining FP time windows (again, I miss the flexibility of the past, when being a little late was okay), BUT keep most your time as flexible as possible.
Try to allow discovery and to appreciate the things that catch HER attention.
That said I've also learned, with a first timer, you can explain the importance of zigging when the crowd zags- but you can't force it. They won't know until they see. Your newbie won't miss the thrill rides, she will be miserable if you impose rope drop on a night owl/1am park touring on a morning person. You can advise quality walking shoes- but if she ignores you, you'll just have to break when her feet get sore. I'd suggest avoiding any line over 45minutes - rather than focusing on trying to see every e-ride.
I'd suggest no more than ONE ADR, ideally AT your home resort to allow maximum flexibility. Unless of course, fun dining is her focus.
One trip we took a newbie on a very slow week- just before a holiday. He simply could not fathom the purpose of all the railings. The end of our trip was the start of a holiday week. Suddenly the parks were jammed- and he understood! Still, he was also dumb. He didn't bring long pants and was miserably cold. (Until we bought him a blanket.)
Another trip, my newbies wanted to swim. I took them to MK. They didn't appreciate anything, until AFTER they went swimming. It was only AFTER swimming- that they saw anything else.
One more newbie could not go with the flow at all. She's an alpha, and just isn't happy unless she's calling all the shots. She was happiest staying at the hotel alone all day!