For how long was a person with novel coronavirus contagious before she started having symptoms? how many days was she already spreading the virus?

Incubation period: The incubation period is estimated at 2-14 days after exposure to the time that symptoms appear. More information may be found on the CDC website: https://www.cdc.gov/coronavirus/2019-ncov/about/symptoms.html

Possibly 48 to 72 hr: People with COVID-19 may be contagious 48 to 72 hours before symptoms begin. REF: https://www.health.harvard.edu/diseases-and-conditions/if-youve-been-exposed-to-the-coronavirus

The incubation period is 2 to 14 days, but may be shorter for the Omicron variant. People are considered contagious 2 days prior to a + test if asymptomatic or 2 days prior to symptoms starting, if there are symptoms. The current CDC link for more information is: https://www.cdc.gov/coronavirus/2019-nCoV/index.html