The equivalent is a woman who finds out her husband has been cheating or has gambled away the kids college fund. = Divorce for any woman *with self-respect*.
You aren't even truly committed to her. Really, you *can* do better than this sad woman. Move on. You deserve it. Leave her to the sad hole she is digging, you don't owe it to her to enable this. As others have said, people take 2nd jobs, etc. to get by. Or... GASP she could have asked YOU for help if she truly loved and trusted you. Just something to think about.
Second thoughts can generally be amended with judicious action; injudicious actions can seldom be recovered with second thoughts.
--Cyteen by C.J.Cherryh