There are no videos or photos that I know of that show transfers. I've tried to do some photos when we have gotten DD into ride cars, but it's hard to take photos since I have to help with the transfer. The best you can probably do is look at the pictures that are available and try to figure out how best to transfer - it may be different for each attraction because on some you will enter from the right, some from the left, etc.
If you can let us know some of the specific attractions you might be interested in, we can give you more specific information. I do have pictures of many attractions on my computer, but don't have them on the internet yet.
Also, if you go to the thread titled "Sue had a great idea", there is a link to a thread for each park where people were asked to post as much information as they could for each park.
There are lots of things she can enjoy without transferring at all - all shows have spots for wheelchair and some attractions have ride cars that accomodate a wheelchair - like Small World, the Backstage Tour at the Studio, the Safari at AK and the boat ride in Mexico. I would concentrate on those.
If she likes Soarin', even though it requires a transfer, that would be a good ride to go on. The transfer is not much different than transferring to a chair; the floor is level with no tracks and there is lots of room so you can position the wheelchair and helpers whereever it works best.
Some of the attractions that require a transfer are hard transfers even if the person can assist (Pirates of the Caribbean comes to mind because the boat is low). Some of those types of rides might be out of the question for her because of the difficulty getting down and then back up again.
For the rides that require a transfer, in most cases, the wheelchair can be brought right up to the ride car (even touching if that is needed). For the rides with moving walkways, the walkway can be slowed or stopped if needed. As you come to the boarding area, let the CM know what you need. They usually slow it, but don't usually come to a complete stop unless someone says they need that. Peter Pan is one to avoid - the moving walkway can't be stopped and the ride car is swinging a bit, not totally stable.
The CMs can be helpful at moving the wheelchair out of the way, but are not allowed to physically assist with transfers (that is for their safety and the guest's safety since the CMs don't know how each person needs to transfer). CMs will move the wheelchair out of the way once you have boarded.
Two other things to keep in mind for transfers:
1) You not only have to get her in, you will also have to get her out. Sometimes the getting in is easier than the getting out.
2) Each transfer has an "energy cost" both for her and the people assisting her. Some transfers (like Soarin') have a fairly low "energy cost". Some (like Pirates) have a high energy cost. Some of the short attractions at MK don't give time to 'recover' from the transfer in before you have to transfer out. Try to balance out the "energy costs" so they are distributed thru the day or you will end up wearing out in the first few hours.