My cat is leaving

so as you can tell from the title my cat is leaving our house as my sister developed an allergy and i dont know what to tell you. i feel so broken and ive been crying for the past three days. shes going to my moms colleauges house but i know that im gonna miss her so much. she was truly the only thing i looked forward to whenever i would come home from school. ive had her for a year now and ive grown so attached and i dont know how to deal with her absence. any tips?