I'm a wheelchair user, rather than visually impaired, but when I flew with AA they were great about my disability. As long as you give them advanced warning, they can do a lot to help. Make sure she calls the airline as soon as possible to talk about her requirements. It would also be good to call a few days before leaving, just to make sure that all the details are still there. Try to request a seat close to the toilets, so she won't have far to walk.
She can arrange for a Skycap to meet her from the taxi ranks, or if you'll be with her, you can arrange for extra assistance to meet you inside the airport. If you let them know in advance, they can take her around the airport on one of those electric cars, so she doesn't need to negotiate long distances, in a strange and crowded environment.
For the security check points, they're always very considerate with me. Make sure her white cane is visible when you come to the front of the line (sometimes they take people with extra challenges through a separate line, sometimes they don't), so they know what issues she has. Even if you get a gate pass, you won't be allowed to go through the metal detector with her; but you could probably ask one of the staff to lead her through. Tell her to wear shoes that are easy to take off, because they usually make people put them through the scanners now.
If they do a pat-down, she will have a female security officer, and will be taken off to one side (still within sight of you, if you're with her), so she won't have people bustling past. They will explain exactly what they're going to do, before they do it; and they will tell her step by step what they need her to do.
When she gets to the gate, she should go straight to the desk. If they're aware of her and her needs, they will be able to make sure things run smoothly. She will be able to board the plane before everyone else, as wheelchair users do, so she is settled in her seat before the hoards descend. A member of the crew will help her to her seat, make sure she has everything she needs, and will make all staff aware of her.
During the flight, if she needs anything, she can press the call button and a member of the crew will get there as soon as possible. If she needs guiding to the toilets, make sure she calls them in plenty of time, as it can take a while for them to become available. I suggest she doesn't try and get anything out of the over-head lockers herself, as bags can shift around and she she might get one fall on her. She should probably have a small bag that has things she needs immediately, which can be tucked under the seat in front; and have a larger bag that has other things, which can go in the over-head locker. The radio system on the plane usually has some good stuff on it, so make sure she asks how to work the controls. If the fasten seat belt sign comes on during the flight, it will make a 'bing' noise, and is usually followed by a Captain's announcement.
When the plane lands, she needs to stay in her seat. There are always loads of people who think they have to be first off the plane, so there is a big crush of people trying to get into the aisle. Once the plane has cleared, a member of staff will come to collect her. She will then be taken up the ramp, to one of the electric cars. She should be able to stay on the car all the way through passport control.
For baggage claim, she will need to get a Skycap to help her. Make sure the bag is very obvious before checking in, so she can easily describe it to someone else. I find coloured ribbon is a nice easy way to do it; tied tightly onto a couple of the handles, it should be easy to spot (try to go for unusual ribbon, such as rainbow or spotty, as I'm not the only person who knows this trick). Once she's got her baggage, the Skycap can take her to the taxi rank, or to someone meeting her.
A few more random tips, just off the top of my head:
Make sure she has some cash easily available for tips and trolleys.
Have her passport, tickets and any other paperwork in the front pocket of her bag, easily arranged so she can find things quickly.
If she has help packing her bag, make sure she is there the whole time, and knows exactly what's going into it, so she can answer the security questions. She will need to tell them that she had help packing, but was present, and hasn't left it unattended since.
It might be good to put things in separate bags, with distinguishing features (buttons, charms, tags, ribbons, etc), so she can find things quickly and easily.
If she's going to carry any liquids on the plane, make sure they're in a clear plastic bag (meeting all the security requirements), in a place she can get to them quickly.
Have a tag on the bag with her name, home address and the address she'll be staying at, so that it can be easily redirected on to her if it gets delayed (hopefully it won't but it's best to be prepared). Might be good to have it in Braille and written text, so she can read it, as well as airport staff.
Make sure she has a change of clothes in her hand luggage, so she can get out of her flown-in stuff ASAP (this is also useful if her bag takes a while to get to her).
Is she going to Disney, or elsewhere? If Disney, there's a whole heap more information we can load you up with!
Hope all of this helps, and if you or she have any more questions, do come back and ask!
It's wonderful that you care so much, and this sounds like an amazing opportunity for her! Of course you're all a bit worried about it; I worried about my first flight in a wheelchair, even though I had someone else with me; just try not to let it get any of you too stressed.
. She has bad memories of that (she was very young, but it made a lasting impression). 
Couldn't be a further from the truth statement. This isn't her first time flying... this is her first time flying SOLO.
