Other shelters will sterilize her. They have a good reason for it. The kitten population is astronomical and the last thing an animal shelter wants is to put five more homeless cats in this world.
But you may have objections against spaying a pregnant cat; after all, it is an abortion at the same time. So a much better idea is to take a pregnant stray woman to a local rescue group. In the US alone, there are dozens of active rescue groups. Not all, but many let the queen have her kittens and find a home for them.
But in the end, perhaps the most satisfactory alternative is to keep the cat and let her give birth. Take care of her. Have a vet examine her to see if she is in good health. And get the right information to be prepared for complications.
And remember: stray dogs are used to going wherever they want. So keep your doors closed. Otherwise, you will adopt someone else.