With a couple of two by fours and some hardware cloth (bigger wire mesh) you
could enclose a portion of the balcony in where she would be safe to view
birds to her heart's content while you were gone. Just make the entrance
through the patio door. YOu can use a piece of plywood fitted in the track
of the sliding door and then fit it with a cat flap. Run the cage as close
to the balcony edge as you can and give her something to perch on.
Attaching a bird feeder to the outside of the balcony railing would either
be catTV or cruel, depending on your outlook.