基本上你不要介入對方的財務糾紛。
加州對於夫婦離婚時的財產分離是使用 community property 製，雖然正常的情況的處理建議如下 (但是因為對方並沒正式婚姻關係，所以老貓不會建議您介入對方的財產糾紛)
In California, when a married couple is getting a divorce and both are tenants who signed the lease, the landlord typically has the option to return the security deposit to either party, or to both parties jointly. However, it's important to note that the landlord is not required to split the security deposit between the tenants. If one party can provide evidence that they paid the security deposit, such as a canceled check or a receipt, the landlord may choose to return the deposit to that individual. It's advisable for the tenants to discuss and come to an agreement on this matter, and if necessary, seek legal advice to ensure a fair resolution.
你的處理方式可以是，誰在租約上就寄給誰，如果雙方的名字都在租約上，你可以開一張聯名的支票，然後寄一個通知給雙方，告知對方你返還押金的總數與支票號碼。要求對方一起來領取，或是由對方以正式書麵通知告知您，對方的決定是由誰來領取，所以讓對方決定要如何處理。
當然，如果你不想要麻煩，您也可以直接返還給當初寫支票的人，(但是你必須保留明確的證據，證明是其中某人寫的支票，不然就不要這麼做)
