Generally, as long as the guest is one of the staying party, Airbnb will hold the primary guest responsible for damages. Since you know she will be leaving a day early, you should send an Airbnb message that confirms checkin and checkout and reminds the Airbnb member that she is responsible for any damages caused by her entire party. Be sure to ask for the names of each person so that the guest cannot deny knowledge of who they left in the listing.
Also, you call them 'girls'. Airbnb requires guests be over 18. Make sure you're not inadvertently renting to minors.
Finally, Airbnb's insurance is secondary to your home insurance, which may not pay for damages. Hopefully you have a security deposit against which a claim can be made if there is any kind of significant damage.
