Hello @Sonja431
Good advice from @Patricia2526 - keep emotion out and remain factual. My guess is that they know they won't be getting a 5* star review from you I would leave it to the last possible moment to post your review as the guest will be notified as soon as you have written yours.
Remember you are leaving a review for future hosts and if your guests leaves you a bad review you will have the opportunity to a public reply just underneath hers that will set things straight. If she says anything defamatory then you may have grounds to have this review removed but that's another battle.
And yes you will be reminded many times to leave a review by Airbnb and you will feel that pressure but just do what is best for you.
All the best
Joëlle