If you are able to establish the above, you may be considered as if you are married and get some or all of the beneifts of a married person. However, whether you will get 1/2 of the assets, I don't know. To answer that, I will need more information which must be done through a in-person consultation.
As for suing her, it is virtually impossible because she didn't do anything wrong. The only way you could possibly sue her is to claim that she and him conspired with each other to take your money. That will be almost impossible to prove.
Good luck.
John Oh
(323) 456-4406
jho@johnohlaw.com