Y'all there is a cat that is pregnant and came onto our porch today and won't leave. Keeps trying to come into my house.…

Y'all there is a cat that is pregnant and came onto our porch today and won't leave. Keeps trying to come into my house. But we can't bring her in due to our other 3 animals. She looks well kept like she is someones cat but nobody is claiming her. She was super hungry. And cold as can be. We put a cat crate outside with a changing table pad and blanket inside and a sleeping bag over it to keep the cold out. Gave her food and water. It's not one of the usual strays that roam our 4 acres of woods/ yard. Other than what we have done, what do we do further to get this cat where she can be taken care of and also her kittens when they are born? I don't want her to get ill/hurt/ or anything along those lines. Scared a shelter won't take care of her. And we also don't have the extra finances to take in a 4th animal. I have 2 cats of my own, one fixed 13 year old female who hates any other animal (even our other 2) and a male who isn't fixed that's almost a year old. So bringing her inside isn't the best option for any of us. Any advice????