Sara,

I know how difficult it is. What you need to do is get a trap from your local pet shelter. Make SURE it has 2 doors. One is the trap end, the other is a lock door you can open and close to feed her. I think that is going to be the only way you can get her, unless you try putting some nasty smelling sardines in a very large carrier with a trail of juice and lumps of sardines leading to it. When she goes in, close the door. Or get a trap. The trap is the best route. If she's hungry enough, she'll go in.

Keep us posted and hang in there!