What do I do?

We found a stray dog near a gas station today. She’s a big girl and possibly pregnant. A local lady said she thinks the dog belongs to a homeless man and wanders the streets. People at the gas station feed her sometimes so she comes around there. Idk what to do our local shelter is saturated with large dogs and they don’t get adopted quick. Its no kill so they’ll take her but if the dogs used to freedom I feel like I’d be putting her in jail at the shelter. The shelter is soo loud and has small kennels. It would kill me to know that she enjoys her freedom and I’m taking that away from her on the other hand I can’t bring myself to release her to the streets where she could get hit by a car….