QB Issue Resolution:

You can remote in to her computer (TeamViewer, LogMeIn, etc.) and work in her QB as long as she is not using her computer.

Resolution for Issue 'If my client has Quick Books on her computer, can I access and post information on her computer from my quick books on my computer?' available: Yes (Solved).
Source: Intuit Community forum.

If my client has Quick Books on her computer, can I access and post information on her computer from my quick books on my computer?: this issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the issue yourself by looking for a resolution described below. If it is a complex issue or you are unable to solve the issue, you may contact us by clicking here or by using other support options.

Support for computer
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