Cat in heat

So my cat is a female and around 6 months old. She recently went into heat about a month ago. We scheduled her an appointment to be fixed but it’s not for another 3 weeks. She’s miserable and is keeping me up all night meowing. Does anyone know if there anything that will soothe her and make her calm down, at least at night time. She’s such a sweet cat, hate to see her like this :(