newly adopted 4yr-old German Shepherd

Question
I just recently adopted a four-year-old female German Shepherd. She is very sweet and we get along well. I am nervous to let her off her leash to run free since she is so new to the environment. She also hasn't pooped since i've had her for the past two days. Is that normal? I let her off her leash this morning and she peeed. Do u think I need to worry about her not coming back to me. She was a lost dog and I don't know how her previous family treated her. She follows me and listens to me so I think she likes me, I am just unsure if she realizes I'm her new mommy. Any advice?

Answer
I wouldn't let her off leash.  It will take a 4 year old at least a month or more to bond with you.  Even then, some dogs can never be trusted off leash.  

I would walk her around on leash.  She can only hold it and walk so long.  When she finally has to go, lavish praise on her.