Cat in heat

Hi ! We're a foster family for a cat shelter, meaning one or two cats from the shelter live with us while we try to find their forever home.

A week ago, a cat of 9 months came to live with us ! She is the sweetest cat. It took a few days before she acclimated to her new home, but she is now very comfortable.

When the shelter told us about her, we knew she wasnt sterilized yet, and that she would be in heat. We agreed to take her to the vet ASAP to take care of that (she also has FIV ans we need to check on that) and we have an appointment next thursday.

At first there wasnt any problem, I guess she was still a little bit stressed and shy, but she has been moewing non stop since yesterday. She seems so frustrated. Is there anything we can do to help her through her heat until the appointment ?