Why is my dog suddenly hiding when i leave the house?

I have a Jack Russell Terrier that is nearly 5 yrs old. She recently started hiding and cowering when my SO and I leave the house. She had never done this before. She came from a previous home where she was mistreated, but she has had nothing but love showered on her at my home. We have had her about three and a half years. She used to jump against the door when we left, but now she hides in the bedroom instead. Does anyone have any ideas as to why she might be behaving this way?

She has recently retired from her pet therapy position, and she has been through obedience classes, and passed with flying colors.