Fortunately, the weather is warming up so she stands a good chance of surviving. Here is a list of things to try to get her back.
1. Visit all vets and shelters in the area to drop off a picture of your bird.
2. Place posters all over the neighbourhood.
3. Place an online ad at: http://www.911parrotalert.com. It's a widely used, very effective place to advertise and get the greatest amount of persons helping you.
4. Place an ad on: http://www.craigslist.com. A great, caring community of pet lovers.
5. Place her cage outside on the balcony, in the front yard, or in front of a large open window. If she sees her cage, she may come home herself. Place her favourite toy and food in plain view.
6. Maintain a schedule of walking the neighbourhood calling her name - birds can survive a long time outside.
7. Investigate all leads. You'd be amazed how far a bird can travel.
My heart is with you - I have parrotlets.