1. Yes my fiancee Dionna does snorkel and I think that would be awesome if she could dl that while I dive! (what would be the cost for her to come along and snorkel during a dive?)
All dive boat operators have non-diver rates which are generally 50-60% of the diver rate. They don't offer dedicated snorkel guides for this rate, so if she's not comfortable snorkeling all alone, then you'd want to consider hiring a guide to go along with her.
2.As far as the best islands....I would love to have some ideas of just cool places to go and see not only for diving. I am very interested in hearing about your day trips via speedboat for diving and snorkeling though.
As I mentioned, you can take ferries to different places from Phuket. Phi Phi is a really beautiful island that's close enough for a daytrip by taking the morning ferry over, spending the day, and taking the afternoon ferry back. Phi Phi is quite small and is on the backpacker trail, so expect a lot of drinking, substance use, all-night beach parties, and such if you decided to stay there a little longer. Ton Sai village is where the ferry stops, and to get anywhere else on the island you have to take another boat. So if you do decide to spend a few days there, make sure you know what you want--isolated resort that's hard to get to/leave or beach party tourist town with hundreds of 20-somethings. The diving around Phi Phi is really nice.
Another island you can get to by ferry is Koh Lanta (by changing ferries at Phi Phi). Lanta is much less spoiled than Phi Phi, and bigger, so you don't get the crowds as much. Beautiful beaches and a road, so you can get around pretty easily. The diving is also very, very nice. Lanta tends to attract a somewhat more mature tourist base, though there are still plenty of young backpackers and therefore a small beach party vibe, but not one that dominates the whole island scene. This island is a bit too far to go for a daytrip. Diving is very nice.
Very close to Phuket is Koh Racha Yai. This island is mostly undeveloped. There are only a few hotels there and one dive op. Diving is pretty decent, but there's no nightlife at all. Daytrips don't generally stop at the island for any beach time or visits, so if you want to go there, I'd recommend overnighting.
There are other islands further south and further north where there is diving, and there are other activities you can do that visit islands on daytrips, such as a bicycle tour of a nearby island, sea kayaking tours of islands with central mangrove bays, flat-bottom boat tours of really off-the-beaten track islands where you can just play in the water with nobody around. It all really depends on what you want to do.
3. As far as private diving trips go...$1,000 may be out of my budget. My biggest concern is being in a small group versus a cattle call style tourist nightmare. I have been happy with 4-8 person groups (including myself) in the past but less is always better.
I figured you weren't really imagining how much it costs to charter a private boat for the day to go diving! Most dive boats here are big, spacious vessels that take multiple small groups diving. Dive guides don't normally take more than 4-6 guests each. The big boats are needed since we dive year round here and little speedboats get swamped when the seas get a bit bigger. In February, though, the water should be mirror flat, so we can probably find a few daytrips on speedboats for you if that's your preference.
4.We were considering staying at the BEST WESTERN PREMIER BANGTAO BEACH. We aren't married to that hotel (or phuket for that matter). So if you have other recommendations for places to stay or islands to use as a home base I would love to hear them. Thanks again for all the help!
Bangtao Beach is one of those far northern beaches I mentioned earlier. It's really too far away from the dive boat pier if you want to do more than one or two days of diving. Look for something in the southern end of the island so that you don't have a 1.5 hour taxi ride (at your own expense) to get to the boat. You might like Kata Noi beach, as an alternative.