Oh dear it seems like she's not too familiar with the platform @Jean174
1. It's incredibly unfair to guests who booked in good faith to cancel their bookings at the last minute to accommodate viewings . She should have blocked out dates for viewings when she knew she was selling
2. If she wants to cancel her guest bookings for viewings she should do so, pay the penalty and the guests will be free to rebook with another host .
She can recommend you as one option
3.Her reviews for her current listing will stay on her profile
the best way to handle the clash is to rearrange the viewing dates if she doesn't want to tarnish her reputation as a host