My spouse disappears after 45 days in this country. Should I start divorce and immigration release of financial responsibility? She has conditional permanent residence status.

The divorce is unrelated to your decision regarding immigration.

She will need to file to prove up that the marriage was bona fide at inception or that there was abuse. You have no details other than she left after 45 days. If you believe she defrauded you, then provide as much evidence to the USCIS, it will be in her file when (and if) she files the I-751 RC.

I would start divorce proceedings and also report it to immigartoin if it was me.

Any idea where she went? If you have reason to believe that she was using you to stay in the country, I'd be consulting someone who knows more about immigration law and divorce.