Trinh certainly has some challenges to overcome. Seeing that all her students are already on-line rather than face-to-face allows her some opportunities. She could create forums for general questions and encourage other students who know the answers to help out. There are often many ‘experts’ who could help with technical issues for example. Also by having a central question bank, answering a question once will likely clarify the same question for other students.
She could schedule an ‘office’ time where any students could join via video conferencing such as Skype. As was done with this course, these sessions could be taped for those who couldn’t make it, but were still interested in the information. (This was very helpful by the way, thank you).
Trinh could have one email account forwarded to the other, creating only one place to check which would also avoid people sending communications to both. She also could use the Do Not Reply feature depending on the information she was sending.
I had a professor who explained that they would be highly active during the week but took their weekends away from the course, so to only expect communication on weekdays. She could choose a time when she is not available for communication.
Students working in groups could be directed to ask questions within the group first, then select one team member to communicate with the instructor and relay the messages.
Using feedback from previous years of commonly asked questions, she could make changes to the course reflecting clarified instructions or expectations.