Need opinion on rescued dog

[Powertec]

We'll i will try and make this short. We rescued a 2.5 yr old Australian Shepherd. We are well experienced in this breed.After a fairly rough 2 months in regards to blowing her coat,not eating and general dislike of our puppy we seemed to get her settled to where all those things were dealt with. She is on quality food(Evo all natural). What i gather is that she was rescued at about a year and then had a few litters of pups and now here she is.She has an appointment to be spayed April 10th.

Sooo all in all she had to fight with the older female dog that the previous owners had on a regular bases for food,attention etc and just basic need to be top dog.I also trully believe this poor girl has been beat..She is very timid and has come out of her shell abit but is still just not an Aussie in any way.She won't really play or chew on anything for that matter...Getting her to eat is still a chore but she does.All she pretty much does is sleep.

So the reason for this is today she has decided that we are afraid of the deck. She was fine with the deck last night but today nope won't do it. She goes out after i pretty much coax her out but she just stands there head down. She has to use the deck as the potty as we are in a brand new house and have no grass front or back yet so it seemed better to replace deck boards than carpet from muddy paws. We have been here a month and never had a problem untill today.

Truly i am at a loss with her. It has been a long couple months trying to get her settled and then this...There was nothing out there last night to scare her no dogs,loud bangs nothing i just don't get it..

Any ideas how to help this girl?