Anxious foster dog advice

Hi! I foster dogs who are anxious but this new one has me stumped. She about three years old, looks like a rat terrier mix of maybe 15 lbs., likes being held, likes people in general, non aggressive, and was a homeless stray for a while. Every time we try to approach her to do anything (mostly to bring her outside to go to the bathroom) she flees. She runs away and hides. We have to track her down and catch her, pick her up, snap on a leash and carry her out. She doesn’t cry or try to bite but it feels like a terrible way to go about this. We’ve tried everything we can think of - treats, positive reinforcement, routine, eft… nothing works but also she seems to be housebroken and has not had accidents. Any advice?