Usually you want 10sq ft, but for short period she could handle a smaller area.I can make her a separate pen it would be pretty small
The pen I have them in is small but she can take more of the run so she is safe
The area my ducks are in is roomy enough
How long should it take for them to get used to her
And how big would her pen have to be
Usually you want to do a week, but sometimes ducks get along sooner. I have had ducks integrate seamlessly with little time and other take longer. If they sleep in a coop, putting her in a crate in the coop with them at night can make it easier. You could always try them together after a day or two and see how it goes. If it doesn't work, stick to slow and steady. Multiple food and water areas also help when there is bullying.