Last year, my family and I found a stray cat and her two kittens at my grandmother's house. One kitten was particularly resistant to being rescued and it took awhile to catch him. I basically ended up sitting a few feet away from his food dish, then very slowly moving my hand closer to him. A few times I just pet him briefly, so he wouldn't get frealed out. After a few attempts I was able to scoop him up and into a secure area in the house. He was a little skittish and liked to hide, so we kept him in one room until we could take him to the shelter. If you have any other pets, you might want to keep them separate until you get the new kitty tested. I hope this helps a bit, although it might be hard to sit out in the cold, lol.
If you do decide to put a blanket outside like misskitty suggested, you want want to use something that smells like you so she gets used to your scent. Good luck!