Okay. There is some interesting science here.
From a fluid dynamics perspective, Covid is transmission is very unlikely in normal circumstances when outdoors as breath containing aerosol droplets with virus is dispersed quickly. Your dd is very unlikely to infect anyone outdoors, particularly an adult, due to the difference in height.
But bubbles are different! They contain concentrated exhaled breath. If your dd is infected, then rather than having the droplets of virus disperse quickly, by blowing bubbles she’s spreading little concentrated spheres of exhaled virus particles, which will disperse only when the bubble bursts.
The other bit of science is that the bubble is made of soap, which destroys the virus, but it’s not necessarily the case that all the aerosol droplets in her exhaled breath would have reached the inner surface of the sphere.
If a load of bubbles burst in someone else’s face then it would be reasonable to consider this as a transmission route, but you’d need to test what happens to an aerosol when it’s inside a bubble (I suspect quite a bit ends up on the inner surface but that’s just a hypothesis).
So I don’t think it’d be unreasonable to object to having bubbles blown at you (I’m quite sympathetic to anyone who’s anxious due to health concerns) and it’s also not unreasonable to blow bubbles if they’re not going to land near other people. Interesting fluid dynamics questions thrown up by this thread.