She probably didn’t have a virus, it doesn’t sound at all like sth virus-like took her. The viruses that affect bunnies are very rare in the USA. In any case, those viruses (myxo and RVHD are rabbit-specific and wouldn’t affect you or your other pets.
She’d been separated from her mum too soon, that can weaken the immune defense (or rather prevent it from developping normally), so the bun becomes very vulnerable. I’m confident that nothing you did caused this. As for other pets – bunnies tend to get along well with other pets once the introduction-phase is over. An unknown dog barking or pursuing and acting predatory can of course be very scary for a prey animal if they’re cornered and have no place to run, and a bunny can be scared to death – but that doesn’t seem like the reason why your little one passed.
She sounds like a beautiful little girl, she must’ve been so amazingly cute. I hope you’ll one day find it in your heart to adopt another bunny.