It does look like she has DSLD. What a shame. Does she have thickening in her pasterns? It looks like her left hind is enlarged in the first picture.
There are only about 3 or 4 scientific/research articles on DSLD. Very very little research. They really need to find a genetic test for it, but last I heard they haven't had any luck pinpointing the genes yet.
There is no treatment. Wedge pads can actually make it worse. The best thing you can do is keep her toes rolled back (mustang roll) and don't let her hooves get overgrown or too long. Keep her comfortable for as long as you can. Some horse will remain sound for a few years after diagnosis, others develop multiple health issues and decline quickly.
They did one small study on the effects of exercise and suggested that mild but consistent exercise and controlling the horses weight (low sugar/starch diet) may help slow progression.
Now there is a lady (Dr. Kellen) selling Jiaogulan (a herb) for it, but the research supporting its use is very slim (no horse or human studies), and I have a suspicion that the lady selling the herb is the same one who started the yahoo group for DSLD. I bought some for my mare, and was not impressed as it was extremely dusty and I really didn't see any difference.
It is related to Marfans syndrome and ehlers danlos syndrome in people. The only treatment in people is the drug Losartan which is experimental. Again no studies have been done using this drug on horses. I think it would be cost prohibitive ($100 a month?). I really wish they would to a clinical trial on it, as the disease is progressive and fatal in horses.
My 20 yr old mare was diagnosed a year ago with this. The original vet missed the diagnosis and said it was a minor suspensory sprain. Since I now know what to look for I can find DSLD everywhere. I'm assuming it is common and most people just don't recognize it. I know one saddlebred with it (age 17 who is hard to maintain weight and extremely lame). I pray my mare doesn't get that bad. Right now she is lame at trot/canter, but comfortable at the walk. I know one Paso who has it, but is still sound for the time being (15-18 yrs old) and goes riding every week.
The early onset cases usually are the worst. I think, like the human form, there are different types (6 types for people with Ehlers danlos). Again different types haven't been identified in horses, but some horses have a very early onset, and others don't have symptoms til their late teens/early 20's.
I wish they knew more. It seemed like something "triggered" my mare's symptoms. One day I came out and her left hind leg swelled way up, a few weeks later, her right leg tripled in size. She was just standing around in her small paddock on rest. That is when I suspected something was really wrong as it was both hinds. So far the swelling has gone way down but not away as there is thickening of the ligaments. She has not had any more major swellings like that first onset. Not yet anyway.
I don't know if you are working your horse or if she is lame, but I would stick to walk-trot, no tight circles, no jumps, no uneven ground, no deep sand. You want to avoid anything that will stress her suspensory ligaments, as if they get any tears in them, they will not heal properly. Just normal wear and tear, even just standing on rest will cause them to continue to fail. Mild, consistent (3x weekly) exercise is suggested as that can help strengthen the ligaments and muscle attachments but is not a cure.
It is just a question of how long you can maintain her and how fast the disease manifests. You could have several years together yet, or just a few months. There is no way of knowing.
Supplementing proper levels of zinc, and copper may help, as will avoiding too much iron. Some people have their horse's blood tested for excess iron, as iron overload may be related. (Again this hasn't been proven).
If you know her bloodlines you should post them, as it is probably genetic. The Yahoo DSLD group has a large listing of bloodlines that are affected.