No good deed goes unpunished, right?
Call Westside German Shepherd Rescue (Downtown LA) and Los Angeles GSR (Burbank)...and ask them both if they have any experienced puppy fosters who would help by taking mom and the pups, with the understanding you'll be taking mom back once they're weaned, and handling her vet needs, and they'll be finding homes for the pups. There are
foster homes that "specialize" in this situation -- what you described is just one of those things that happens sometimes, as stray dogs get knocked up before they are recovered, and they sometimes can't be spayed right away for various reasons. Shelters that don't put Fs on the spay schedule until they have an adopter encounter this situation a few times a year (they just come in to work in the AM, and she's given birth in her kennel overnight). So there is a network of neo-natal puppy fosters out there. They're always ecstatic when mom is with the litter and "helping," as it makes the foster family's job so much easier.
Letting one of the rescues handle finding homes for the pups is really important because statistically, puppies have sky-high return rates in rescue. It's much harder to find good homes than you might guess...even though everybody thinks
they want a puppy. Doing home checks, reference checks, and proper placements for a whole litter is incredibly time consuming. Even doing all that, the chewing and mouthing often causes well-meaning, inexperienced people who've never raised one to bail. The pups will need a life-long safety net so that they never end up in a shelter. Well-established rescues can provide that -- you didn't sign up for it and shouldn't have to worry about calls a year down the road that someone's bringing a now-grown dog back. Ask the rescues for help.