Ongoing - track your velocity.
Document every roadblock and inefficiency, caused by her or otherwise.
Bring them up in the Sprint Retrospectives, speaking in neutral language - trying to find solutions to problems, not people.
If no solutions can be found (and implemented), then you need to do two things: start working these inefficiencies into your ...
She does not give acceptance criteria
This is not a problem if the Product Owner is happy to talk through the stories with the team and clear up any details. The team can even create their own acceptance criteria as a result of the discussions if they find that useful.
If the Product Owner is not willing to spend the necessary time explaining the stories ...
It depends on what you consider "mandatory prerequisites to start a Sprint".
When it comes to the timing of the start of a Sprint, the Scrum Guide says that:
A new Sprint starts immediately after the conclusion of the previous Sprint.
There is no decision to start the Sprint. One Sprint ends with the Sprint Review and Sprint Retrospective and the next ...