If it is a tendon or ligament issue, you are correct in thinking that it is just going to be time. The rule of thumb (you may not want to hear this but) is one month of rest for every letter on the word. So it could easily be 6-7 months of recovery. Now saying that, it could be less time depending on the severity of the T/L injury and without knowing for sure what is going on and not knowing how bad the tear or strain is, and without spending a ton of money on Diagnostics (like nuclear scan, x-rays, ultrasounds, etc). Your best bet is to take it slow. Stall rest using your anti-inflammatories and slowly weaning her down and off of those. Then start out with walks 10-15 and slowly build up the time then do a little trotting in hand, and so on and so forth. But you really need to give the horse that rest period of a couple of months before working to much and that means no turn out where she can blow up and do more damage. Also having your vet check her periodicaly during this time, doing flextions and little lameness exams to check her progess. I don't konw how many times I have seen someone get in a hurry and start a horse back to soon and do more damage or even something more permanent.

Now when it comes time that you start riding again and you want to strengthen those tendons and ligaments across the stifle and patela area so that you don't have the problem of her stifle locking you will want to find a good footed arnea. Lots of walking and trotting in 6-8 inches of sand, lots of collecting exercise, up and down hills at a walk frontwards and backing up hills, and if she will let you drag off her, dragging a tire or a log. This makes them really use their hind quarters and strengthens that area to keep it from locking up. Doing this 2-3 times a week for 20-30 minutes will be great for her.

Hope this helps, Good luck