Hello again Mark and thanks for waiting.
Sorry to hear about Bella's problem. Hopefully this will be something very minor though, as you say stomach upsets are very common when a dog goes to a new home, however I have worked out an answer for you, please read it through and see what you think ...
Firstly because we are talking via the internet I have to say that this sort of thing is always a gamble, so if you want to be 100% sure you are doing the right thing you should have a vet check Bella over ASAP.
However that said that there are a number of home remedies for diarrhoea in the dog, these often work well in uncomplicated cases where a dog is otherwise fairly bright and happy, where for example a dog has eaten something she should not have out in the yard, or some unaccustomed new foodstuff, or has a minor tummy bug in a new home as in your case.
Here are some examples of suitable home remedies you can start with ...
1. Some owners try and control the situation with diet alone before they try anything else. This is logical and often works, the basis of this is to give the intestinal tract a complete rest and then bring it back slowly to function, resting the alimentary tract is the critical factor. It would go something like this ...
A. Starve her for 24 hours but make sure she has access to water.
B. The next day feed her four or five small light meals in the day. These meals should be the likes of chicken, fish, scrambled egg etc. with a little rice.
C. If she picks up on this diet gradually reintroduce her normal diet over the next few days.
2. Live yogurt added to the food can often help. Some gastro-enteritis situations are caused by an imbalance in the bacteria in your dog's gut. Live yogurt is full of " good " bacteria and will seed them into your dog's intestinal tract and restore the balance. You do not need to give much, say a tablespoonful twice a day.
Of course if any of the above does not quickly start to work or if Bella deteriorates further in any way you should see an ER vet without delay just to be on the safe side.
I hope I have covered your question fully enough but if you would like further clarification or to talk things over a bit more then I will be on-line for the next hour or so and I will be more than pleased to continue working with you.