Some of the silk orchids look pretty realistic. However, I do think that the interest is in living orchids. :)

Yes, Leafmite! I just figured there must be something at the opposite end of what I look for that might work in her conditions. A living plant that flowers can brighten one's spirit!

After all the comments, a plant stand with grow lights looks to be the best for this environment.

If you look on Amazon for T5HO lights, a two foot, two light lamp is not that expensive (when considering the price of orchids). I couldn't fit all my plants in the windows so I ended up getting one (second hand) and now have it hanging from a self-standing clothing rack (which was really cheap from Walmart). It doesn't take much space and is the right height. You could also buy a set of shelves, too, which is what I did for most of my orchids.

You are in Tucson, Arizona....where is your sister's dark and damp garden apartment located (or grow zone)?