Posting here again about my cockatiel Bella on a separate account

earl: long story short, we took her to the vets a few days ago because she was shivering, vomiting and doing splattered brown poo. She was left in their care for a day and a half, being force fed antibiotics etc. They gave her back to us earlier than intended thinking she was healthy, only for us to find that she was still shivering and pooing pure water.
We took her back to stay for another two days and now they've assured us that she's healthy and doesn't need anymore care. It turned out to be a bacterial infection (or a mixed growth, as they called it).
I can't help but worry though - since she's come home she's still been doing runny poo and is spending a lot of time sleeping. She's definitely far brighter and more excitable than before, but could there still be something wrong? I even noticed her trembling a couple of times. I'm hoping she's just adjusting to being back home and is still a little stressed.
Answers would be much appreciated!