I can't look at that site anymore.
I was going to say that I am not sure a rescue group would necessarily agree to what you were suggesting, BUT most would at least be willing to post her picture and bio for you on their site (as long as she were already spayed). But I'm glad to hear she has been adopted!
For future fostering, you could check out your local rescue groups, which you can find through petfinder.com. Even with an all-breed rescue, you could specify that you were only interested in fostering Chihuahuas and see what they say. Of course, applying to be a foster through CRT might be your best bet, since it is a Chihuahua specific rescue.
One more thought.

Getting involved in rescue transport could be an easier alternative to fostering, and it is no less important. I have done this a few times, and I love it. It is smaller commitment, can be done around your schedule, and is good for people (like me) who are unable to commit to fostering at the moment.
Just in case anyone might be interested, here is a listing of nation-wide transport groups:
www.bostonterriertn.org/Snap%20Marshall%20Emerson's%20Transport%20Page/Nationwide%20Interstate%20Yahoo%20List.html
ETA: I don't know what's up with the link, but copying and pasting it into your web browser ought to work.