There are two different issues here.
Not wanting to potentially spread norrovirus between households really isn’t unreasonable,and illness can’t be helped. So from that perspective the outcome was unavoidable.
But perhaps the more concerning thing here is that your DSD ha a separate relationship with her father which doesn’t include you and her siblings. What’s the genuine reason for that?
My DS has a similar issue with his dad, he sees him one-one and has done pretty much since he was fourteen, fr the simple reason that he doesn’t feel welcomed by his dad’s new partner and her DC, and as consequence he has almost no relationship with his siblings on his dad’s side unless his dad brings them along, which he very occasionally does.
you’re clearly not a blended family, and that is something which you should be addressing IMO.
It’s fine for DSD to spend one-one time with her dad, all kids should.
But the point at which they’re spending every weekend together just the two of them, even going away to hotels at the exclusion of her other siblings isn’t something any of you should be aspiring to and which should be addressed.
The risk you run here is that DSD will stop coming altogether in a couple of years, as my DS has, and the relationship with her father will also suffer as a result.