Op, you/your daughter absolutely made the right decision. It's ridiculous that anyone else says otherwise.
Regarding quarantine, we don't have a good answer for those that are vaccinated. However we know that the vaccinated generally have shorter courses of illness, and therefore clear the virus faster from their body. In an unvaccinated person, the absolute longest they are infectious to others is a little over 9 days - so quarantine period was set at 10 days.
For someone who is vaccinated, I don't have a perfect answer, but I would imagine 7 days would be sufficient although potentially even as short as 5. The average time to clearance of the virus is about 5.5 days.
If she was truly asymptomatic, then count her first positive test as time = 0. If she had any symptoms, I'd call that time = 0.