Young Female Tabby Cat

Very nice young female cat showed up on my back porch about four months ago and has never left.
I have tried several shelters and all are full.
I have also tried bringing her into my home, but the cats I already own are having no part of it and just scare her back out the door.
It is too cold for such a sweetheart to be living this way.
Please contact me with any interest or if anyone knows any rescues that could possibly have room for this poor girl.
Thanks so much in advance!