Although I can't speak from a DM candidate's perspective, I really enjoyed myself at Ban's Diving Resort. It's definitely a big shop, a diver factory isn't a bad description, but I don't feel you miss out on high quality, personalized instruction. I tagged along while friends progressed through DM training and can honestly say the CD and and staff instructors take the program very seriously.
From a social aspect, I really liked (sometimes) knowing 20+ candidates... it made for really fun evenings at the Fishbowl, the bar / restaurant / occasionally outdoor classroom and one of the more popular spots in that part of the island. Snorkel tests are tons of fun. I did find that you tended to mix mostly with other divers from Ban's, and by the end of my stay I felt it was pretty clear a lot of divers from other shops felt Ban's is a bit of a clique. You don't really notice it while at Ban's, as there's so many divers to get to know. While getting your bearings, it's a really simple place to start your Koh Tao adventure at (good accommodations and decent food and consistently fun parties).
As new candidates arrive every few days, it allowed plenty of opportunities to get through course requirements at your own pace. They have a really great internship program and former candidates dive free on return (providing they DM). They seemed to have the biggest 3-boats on the island which to my recollection almost always had space for candidates. The boats are really comfortable, with a giant dry table and upper decks great for dive briefings. 1-boat shops would worry me a little, as boats do break down.
I arrived planning to stay a few days to complete my AOW but wound up staying for almost a month, completing my Deep, Nitrox and Wreck specialties and then my Rescue Diver. Pi Wan (resort manager and part owner) is fantastic. She sorted out accommodations and then eventually flights etc., and really took care of me while I was there. I don't recall if DMT's get free accommodations in the fan rooms, but there are plenty of inexpensive and decent places near the shop.
I dove with a few other shops for occasional fun dives and had mixed experiences. The vibe at Good Time was amazing, but it's really small, and I'm not sure I'd love to be in a program with only a couple other candidates. I met great people from Big Blue, but never went diving with them. Buddha View was a bit of a hike from Ban's so I never went, but I heard good things and see they are affiliated with Utila Dive Center, where I think I'll be doing my DM. I dove once with New Wave, and on that trip their boat broke down on our way to Sail Rock (kind of a downer). They did give us partial refunds, and kudos to them for making it right.
If your daughter is looking towards IDC, I think Ban's would be a great spot... They have a ridiculous amount of OW and AOW classes happening every day, so there's a huge demand for divers looking to gain experience assisting classes.
There may be better programs out there, but I know if I went back to Koh Tao, Ban's would be my first choice.