I feel stressed for her, why would you leave it so late to go home? It's not like she can just hop in a car and drive back home. My uni has specified the 3-9th window, with safety and wellbeing measures in place if you have to stay a few days longer than that or over Christmas because of flights or trains being booked already or if you're covid positive.
She has a whole border to cross, and it will be so close to Christmas. With how precarious everything is and the fact Berlin is under a lockdown....surely you would just want to be safe and go home as soon as possible? Even from a selfish perspective disregarding other people's safety, it doesn't make sense?