Hi and
My Tetley is like that too. He's 6 months old and has always had a sensitive tummy. I've just accepted the fact that that's just how he is! I had him tested too and nothing showed up in the screen.
Maybe Chica needs a change in diet. What are you feeding her right now? Once I started adding Missing Link to Tetley's meals I found his digestion got a little bit better. He still can't eat bully sticks though, or he has an upset tummy afterwards.
I've just tried to keep track of what Tetley's triggers are so that I can avoid them. I hope Chica feels better soon.
As long as she's still active and playful, I wouldn't worry about it too much.