Agree with vets trip, without a doubt. Did she soil in parents house at all? How did they handle it if she did?
I would just go back to basics with the toilet training, if she knew it before she went away when she also had the illnes, now she is back she still has the illness but has lost toilet training i think it just needs re-training.
Bare in mind she is a little bit older now and could perhaps be feeling slightly better so they calm puppy you had could have just been her age and illness, when they are young they sleep a lot more then all of a sudden dont need the same sleep and have more energy.
Let us know how the vets goes.