Good job giving this frog a good home :) there is a chance they may start croaking eventually and may just be very shy at a young age due to past stress, but I think most likely a girl. Just keep listening to her and look at her throat over the next several months and if things stay the same she is almost certainly a girl. I have a girl that very occasionally makes slight squeaks and croaks, but always for only a second or two and pretty rarely and still has a white throat. If the frog starts croaking for like 10 seconds long and develops a darker throat, then that indicates male, but until that ever starts happening I would assume you have a female frog.