Possible that she's just stunted then. Since she was so sick during a time she should have been growing.
In my experience, animals with failure to thrive are never fully out of the woods. I had a rabbit with it that did great for 4 years and then suddenly went down hill and died before she reached four and a half. I have a goat that is almost six that has it and she has gotten incredibly, severely sick nearly every year to the point we had to consider culling her before something wound up working.Failed to thrive, though she is doing greate except size wise. She kept up weight and growth with her broodmates until she got sick. That's when she started to lose a lot of weight. She stopped eating for a while. We thought she would die but she ended up being the only surviving two of six. She is now eating well, keeping a good healthy weight for her size, is active and always happy to see me. So if it is that is she out of the woods? I honestly don't think she'll ever be a typical size silky.
^^^
If it's just that she's stunted, then odds are that she might do just fine.